I haven't lived in London for many years, but I like to browse comic shops when I'm down there from my home in Edinburgh.
London does sort of have an area clustered (or at least strung out) with second-hand bookshops, namely Charing Cross Road, though I don't think many of them sell comics.
However, most of the comic shops that come to mind are more or less in the same area of central London and you coud certainly walk between them, taking in some sights as you go, or zoom between them by short bus or tube rides very easily.
Others will know many more places than me, I'm sure, but here are the ones I can think of:
There's a nice smallish comic shop in Great Russell Street, almost opposite the British Museum. I think it's called Gosh. (And you can visit the British Museum while you're there and pretend you're in The Yellow M
, if you're into Blake and Mortimer! Well worth a visit anyway, of course, and free.)
There used to be a small comic shop in Denmark Street (I think), which may be still there. I forget its name, but London-based forum members might know. I remember it being good for old second-hand comics and second-hand or out of print comic books.Edit:
I've just thought to do a Google check on that Denmark Street one and have discovered that a) it was called Paradise Alley, and b) that it's sadly closed down. Sorry for whetting your appetite needlessly!
For new stuff, Foyles Bookshop in Charing Cross Road had an impressive comic book ("graphic novel") section last time I was there. And there's a Forbidden Planet in New Oxford Street.
And of course, there's the Tintin Shop in Floral Street, Covent Garden.
On a slightly related note, there are a couple of comic/cartoon related exhibition on in London at the moment, which I'd clocked as things to try and see if I find myself down in London soon:
The Cartoon Museum in Little Russell Street has a Viz exhibition, running till January, marking that comic's 30th anniversary. Their general exhibits also include lots of old comic strip stuff.
And the excellent Chris Beetles Gallery in Ryder Street ( http://www.chrisbeetles.com/
) has a British illustration exhibition, also running till January, which appears to include plenty of cartoon work (Heath Robinson, Thelwell, Giles, etc) along with book illustration work. Probably not comic strip stuff, but maybe of related interest anyway.
Lastly, if you're into old Commando comics, the comic's publisher DC Thompson has been bringing out big fat compilation volumes of old Commando Comic strips for the last few years. They're available at most big bookshops in the UK. (I think they've been doing pretty well in the difficult-to-buy-for dads and uncles Christmas present market!) You may already have known that, and maybe you prefer the feel of the real old comics, but I thought I'd mention it anyway.
Anyway, I hope that all helps. I feel quite in the mood for a London trip myself now!