I've just come back from a short weekend in London, having a few "sociable beers". While I was up there I took a little time out to do a spot of shopping (well, the selection is much better in the city than it is in the middle of the countryside where I live).
I took a few minutes to visit CEX (the Computer EXchange). The shop in the centre of London, in Rathbone Place, has a neat Retro exchange, but I was a little saddened to see a distinct lack of ZX Spectrum wares. Perhaps I was looking in the wrong place in the shop, but where they did have loads of ZX stuff, there now was none. A shame.
I almost bought a Neo Geo Pocket Color, tho'. A snip at <30 quid. Pity the games were the same price.
Anyway, regardless of where the ZX stuff was, this shop's a good place to look if you want Retro gear. And you happen to be in London.