> Don't go [to a hi-fi store] with casual clothing, and try to speak in say a more fancy accent/dialect, usually they'll see you as coming from the upper class and treat you better

I doubt this would have worked - social attitudes in England are horrendously complicated. People putting on airs and graces to curry favour tend to be laughed at if the ruse is spotted, and even though the class system still limps on, the vast majority of British people value authenticity over artifice. Moreover, there is not a direct correlation between money and class here, even though they undoubtedly have feedback loops; people becoming immediately richer does not generally elevate them.

The class dynamics between me and Ball Scratcher make for intriguing speculation. He's probably wealthy, but his manners and attitude were rough as old boots. In class analysis terms, the seller would likely be regarded as "working class made good", and his vulgarity as "new money". I'm fairly gently-spoken, and my BBC English voice is sometimes described as "posh", but paradoxically I wonder if that caused additional resentment.