Pete, before you spend a fortune on a mike, try one of the tiny single-point stereo mics from Henry's Radio/Electronics in Edgeware Road - about 200 yards north of the tube station on the right - it shouldn't be difficult to get to from where you live. You can find it from this page (it won't let me give a direct link to the detail page for some reason) but click Microphones, then scroll down to Tie-Clip Microphones and select 173.623 STEREO TIE CLIP MICROPHONE. I've use one with my mini-disc recorder for a couple of years and it gives a great sound. I've even made an extendable holder from a telescopic arial which means that I can point it towards singers in sessions over other people's heads. The Recorder, Mic and Holder all fit in one small case. At under £16 it will hardly break the bank.

On bit of advice, if your recorder has a manual recording volume control, you will get much better results from using it. If you use automatic, the control will "hunt" when the volume is low or where there is a gap and you will get hiss on the recording at maximum volume.