During a brief visit to London, I went to several bookshops on the road in London leading from Leicester Square to Oxford Street: Charing Cross Road. There are at least three major bookshops for new books - Foyle's, Blackwell's and Borders, plus a variety of second-hand, e.g. and remainders ones. I also visited the medium-sized Waterstone's on Oxford Street near the Tottenham Court Road Tube station, and Daunt's on the Fulham Road.
Regarding translations, the situation seems marginally better then when I was in London before.
I did actually find a few copies of the Estonian novel by Mati Unt called "Diary of a Blood Donor" (translator: Ants Eert) in a couple of these bookshops, and found an Icelandic and Polish novel in translation on a display table in Daunt's. The Penguin Classics series has quite a few older works, and these are, of course, available everywhere.
The display table in Foyle's had several translations in the Vintage imprint (part of Random House). I can't remember the titles, but there were several, from a variety of languages. And in that bookshop was even one copy of my own translation of "Treading Air" by Jaan Kross. There were quite a few translated collections in the poetry section there.
But I still think that London bookshops could draw much more attention to those translated novels and poetry collections that there are, by having maybe theme weeks for countries or language areas, e.g. a Portugal & Brazil Week, or one for Scandinavia.
We're not out of the wood yet, I feel.