not to stereo-type here Chris, but what with you being French and living in London an all, I expect you know Kensington pretty well, non?
Now I hate to give this secret away but I haven't had the chance to get down there in over a year, but at the Worlds End/Fulham end of the King's Road is a little triangle of charity shops, Marie Currie/Oxfam/help the aged IIRC.
Oxfam bags up the donations and send them to a central sorting centre but the other two sell the stuff that is donated to them directly. There is also a small road on the Brompton end of the Fulham road, behind the French school where there are a couple of small french cafes (cant remember the name of the road)that has two very good charity shops.
This means some very very rich peoples hardly worn clothes at charity shop prices.
Razors however, I didnt see.