How do you buy trad gear?

Iv been climbing for a few years and have got quite into trad climbing but don't have any gear for myself (iv just been stealing my friends rack) and I am looking at getting my own stuff. The problem is I have only ever bought full price gear from shops but I have been told you can get stuff cheaper online. Does anyone have any recommendations for websites that sell climbing gear that do good deals. (I'm in the UK)