I've just left San Francisco, am currently in New York, and will be arriving in London on the 21st of September. I plan to live in London at least through the end of the year, but probably not any longer than my six-month visa.
I've been all over Gumroad, but not only is the site an absolute nightmare, design-wise, most of the ads I'm finding in the flat-share section are sleazy at best and scammy at worst. London's Craigslist community seems to be pretty similar.
Maybe this is just an American thing, but aren't there any sites in the UK where people post ads like, "I/we are X type of people living in a place that is Y. We want a roommate who is Z"? I've always found that to be the best general mode for finding a place. Lots of pictures, lots of friendly description.
To tie this thread more directly to design talk, I'd also like to hear what your favorite London design-related resources/places/communities/etc. are.