There seem to have been a few people on here recently looking for running clubs, so I thought I'd post this for anyone interested. It is what seems to be, a fairly definitive list of clubs in different regions of the UK.www.runnerswebuk.com/club_ind
The main site has a reasonable race diary on it as well that you might find helpful, although it isn't as comprehensive as the one on this site.
For London based runners, the serpetine RC page is really good and has a separate list of London running clubs.www.serpentine.org.uk/links
Hope some of this is helpful.