I used to cruise them all -- it was my hobby! Find something I liked and take it home for a good wash/mend. If it didn't work out, I could just re-donate it. Oxfam does tend to be a little pricier but I would start there and work along the street from charity shop to charity shop. Miss that.
Love, love, LOVE the charity shops! (love a bargain)

Oxfam was a bit pricey, but they tended to have slightly more fashionable items. I remember just after I first moved there was a big deal about them auctioning off Kiera Knightley's dress that she had worn to the Oscars or some other awards show. Remember, Oxfam does online auctions too.
There was also a British Red Cross shop near us in Reading. A bit of a treasure hunt there, but worthwhile. I particularly liked them for picking up sweaters cheaply for winter since I didn't have many. I scored a great Laura Ashley top as well as some nice, warm M&S sweaters!
Don't forget about eBay! I got a ton of stuff there. You have to know your sizes in the different lines though. Per Una (from M&S) was one of my faves. Principles was nice, but they run small! The thing is, you can pick up items for £1 and shipping is usually really reasonable. And if you find someone who's having a clear out you can get multiple items with shipping combined. Score!
