I went out with frienad recently, who told me to bring my camera along. The reason, was so that I could try out a couple of his lenses.
I instantly fell head over heels in love with the Canon EF 100mm f/2.8 Macro.
I managed to find it second hand for £199 here: http://www.mpbphotographic.co.uk/used-equipment/used-lenses/
I have to say, my experience of their site and service has been great!
They clearly listed out the damage on the lens (The button for changing the focus limitation has gone, and is stuck on Full, which I wouldn't have moved it from anyway).
It ordered it on Bank holiday Monday, and it arrived on Wednesday. Which is really next day delivery.
It was packaged very securely. It works perfectly.
I haven't had a chance to test it out properly, so I tool some low-level light shots in my living room.
Being so used to keeping the 'nifty-fifty' on my camera, it will take a while to get used to the weight and length of the 100mm, but I can't see me swapping it off my camera any time soon.