Having said that, there are some bargains to be had in the comic shops. Gosh! have a nice bookshelf of cheap trades on offer at the mo. I bagged Nixon's Pals for £3, and was sorely tempted to buy a lot more.
If you haven't already, then you MUST get your arse down to the shop and snap up the first three issues of James Kochalka's Superfuckers which are on the discount shelf for a ridiculous £1 each! Honestly imaginary web pals, Superfuckers is one of the greatest comics EVER published and it's got a fucking ace theme tune. You need it.
If Marvel and DC back issues are more your thang, then you might consider braving the shabby world of Comicana...
I've made my thoughts about this place clear in the past, I'm not a fan. It's poky and overpriced, BUT it does stock a lot of old comics. With 50% off those ageing floppies, there will probably be a few bargains to be had. Address here if you want it - don't get too carried away though, you can still pick up most of Comicana's stock cheaper on ebay.
In other central London comic news, I made a short trip to The Comic and Book Exchange on Berwick Street. If rifling through a chaotic mess of back issues and old magazines is your bag then you'll like this dirty hole in the wall. It's choca with bronze and modern age back issues many of which are priced at £1. I couldn't find anything worth buying, but you may have more luck. Directions and a couple of reviews here.