Ahh.. I remember it well. Going to WH Smiths in Liverpool for my first ZX-81. A whole 1K of fascinating bliss. Entire evenings were lost with that computer.
It was soon upgraded with a Memotech 16K RAM pack, less wobbly than the Sinclair item so protracted games of Mazogs and 3D Monster Maze could be enjoyed.
After that, the natural progression was to a 48K Speccy, bought from Rumbelows. This only lasted a month or so before it went wonky and apparently there being a bit of a shortage for replacements, so the deal was I could swap it or another machine, the choices being a Dragon 32 or an extra chunk of cash for a C64. Being not exactly wealthy, buying all the above took a shedload of saving up from my milk round, garden chores and washing cars, and besides I was pining for *anything* computery at the time, I got the Dragon for the time being. Still fun, but felt a bit left out as my mates had Speccys, so a bit more saving, swapping and changing got me back to the Sinclair side of things.
Besides, at my school at least the C64 wasn't *that* popular compared to the Speccy. I suppose working class Liverpool where I grew up was not exactly awash with spare cash and with the 64 being the more expensive (from what I remember) option the ZX was the popular choice. It turned into a bit of a class thing, us commoners had Speccys whilst the posh kids had 64's or, *deep breath* BBC B's with esoteric devices like dedicated CUB monitors and floppy drives.
Ahh.. The distinctive rattle of a C90 cassette in a blazer pocket. Bring a nostalgic tear to a glass eye, that would.