Retail unpleasantness

Something odd has clearly happened to me recently, perhaps some switch has been flicked in my brain, or some chemical imbalance means I'm generating a new kind of pheromone. But either way, as of two weeks ago I appear have lost the ability to shop peacefully: I can no longer buy things in any kind of retail establishment without some kind of minor run-in or bizarre set-to with the people who work there.
I have no idea why this is, but lately I have been unable to conclude even the most simple purchase that involves any human interaction without a problem. I find it a little bewildering - previously I have managed, for some 30 years now, to successfully buy an extensive range of items in a wide variety of shops without so much as a raised voice - but lately there have been a spate of 'incidents' and I'm rapidly coming to a worrying conclusion: something has happened and now all of the people who work in shops are out to get me.
Let me present the evidence, and my calm post-event analysis, and you can decide:

Case 1. WH Smiths. I am queuing for a newspaper. I get to the front of the queue, and place my copy of The Guardian on the counter. The woman serving 'tuts' aloud at my choice, looks me in the eye and says "Bloody Guardian, eh?"
I am completely at a loss to know what to say, so pull a sympathetic face and nod mutely, as if to apologise for my choice of Saturday reading material. She jabs a calloused thumb at a stack of Terrys Chocolate Oranges, and explains that they are half price with any newspaper - but before I can say anything, she adds sneeringly "But you won't want one of those if you read the Guardian" and simply rings up the price of the paper.
Calm, post-event analysis: Now, although this was faintly insulting in a kind of unspecific way, it was actually far more random and confusing than anything else (I mean: what? And furthermore: Eh?) so I have mentally filed the incident away as an encounter with someone not in full possession of their faculties, like the time I encountered a drunken tramp with apparent Tourettes Syndorm, who called me a "cock-smudger": unpleasant, sure - but it would be largely pointless to take offence.

Case 2. B & Q: Later the same day, I am queuing to buy a bungee cord and a bag of screws in my favourite soulless hardware depot. When it is my turn for the malignant till-jockey to serve me, he rings up the items and the total comes to £6.16 - and I then find that all I have in my wallet is a single £20 note.
"One second", I offer, "I'll see if I have the right change."
I begin to turn out my pockets to look for coins. He looks on in almost total disdain, as if I have soiled myself. I manage to scrape together £1.16 in small change, including my only pound coin, and hand it over with the twenty pound note, whereupon he promptly hands me back £14 in change.
"Um, I think it should be £15 back..." I say, apologetically (Apologetically! Why? He's the one that can't count!)
"£14 back, it says here" he replies, pointing at the receipt.
I look at the receipt. He has entered £20.16 as the amount tendered.
"Well, it would" I explain, "because you've typed that in. I think you've entered the wrong amount..."
He looks at me like I am retarded. "I haven't" he says.
"You just watched me ferret around in my pockets for the odd coins..." I say, swiftly edging out of 'apologetic' and into 'aggrieved'.
"Here, sir", he explains, "It says £20.16". He then takes a pen from his pocket, and actually circles the amount on the receipt, presumably so that I can better see the magnitude of my folly. The combination of the false emphasis on the word 'sir', and the use of the pen has me digging my fingernails into my palms with fury, and I close my eyes for a fraction of a second to enjoy a brief fantasy interlude where I take the sodding pen from his pocket and plunge it repeatedly into his heart.
"It says that", I manage, masterfully containing my rage, "because that is what you have typed in. It will say whatever you typed in. Even if it is wrong."
"I typed in what you gave me" he says, becoming slightly hostile.
I shall draw a veil over this one now, the rest is all noise and fingerpointing. It is enough for you to know that it ends with him accusing me of 'trying it on' and me walking out of the shop, inflamed at the injustice of it all, shouting over my shoulder that he could keep the missing pound if it meant I didn't have to spend a second longer in his idiotic presence.
Calm, post-event analysis: I have been wronged and he was an assclown. The fact that I found a mysterious pound coin, loose and unexplained amongst the lint in my pocket some hours after the event, signifies nothing. I suspect we shall be looking exclusively to Homebase to meet out hardware and DIY requirements from now on.

Case 3. ToysR'Us: Sunday, and an abortive attempt to buy a Christmas present for Amelie - her mother has ascertained that the thing our eldest wants the most in the whole wide world is a Little Mermaid 'Ariel' Doll, so that should be what Mummy and Daddy get her for Christmas. Sounds simple, doesn't it? And yet this simple task has proven beyond me: I have spent over 20 minutes in the Disney Princess aisle, gently grinding my jaw in frustration, holding up various packets and frowning at their contents. Why are there so many 'Little Mermaid' dolls to choose from? Which one does Amelie want? Why is this one twice the price of that one, and yet seems identical? This third one seems to have miniature charms attached to her dress, will Ami like that? Or will she simply leave them on the floor for Neve to eat, so that they pass through her body unharmed, to arrive twinkling in her nappy a few days later? This one comes with a small plastic lobster, but carries a high premium for such an indulgence - should I get it anyway? If I don't, will the absence of said plastic lobster on the day ruin Christmas? Why does this 'Little Mermaid' doll have a completely different face to this one, even though they are presumably supposed to both represent the same character? Which one is the right one?
It all proves too much. I decide Nini is better equipped to choose 'Little Mermaid' merchandise than I am (what with her being the Queen of the Sea, and all) and stalk off to the tills to pay for the one item I have successfully shopped for: a plastic tiara, a small gift for Amelie to replace the one that Neve systematically broke into pieces and left on her bedroom floor a few days ago.
I have zoned out and am staring vacantly at the bumper packs of batteries next to the checkout when the girl on the till coughs discreetly to get my attention.
"And what are you supposed to be?" she asks.
I have no idea what she means. Confused, I hold up the plastic tiara, as an explanation as to why I have arrived at her till.
"A tiara? Not very rock and roll, is it?".
My continuing confusion must register on my face. She nods pointedly at my clothes. "Rock and roll stars don't wear tiaras" she explains.
I look down at my clothes. I am wearing a T-shirt with a picture of a car on the front, and a leather jacket with a Remembrance day poppy tucked into the breast pocket. My belly is hanging slightly over my belt, in the traditional 'muffintop' display common to all browbeaten fathers. Conspicuously absent from my outfit is a Fender Stratocaster, a clip on microphone, traces of cocaine around my nostrils or in fact any indication at all that I am 'meant' to be a rockstar. I wonder briefly if she is drunk, or is perhaps high from huffing childrens glue in the warehouse.
"Um..?" I begin.
"Give it here" she says, ringing it up. "Do you want a bag, or will you wear it home?"
Calm, post-event analysis: Again, confusing. Slightly more hurtful than the WH Smith lady, because it seemed less random and more personal. Unpleasant connotations with the 'Will you wear it home?" remark. This incident caused me a second wave of personal grief, because as a result I felt compelled, when I got home, to ask my wife if she "thought I looked like a rock star today" and her mocking laughter is even now still ringing in my ears.

And there you have it. Coincidence? I think not.
As a result, I'm done with shopping: if you were hoping for something for Christmas from me, and it's not readily available from the Internet for home delivery, then I'm afraid you're out of luck....