In reply to jbrom:
Thanks guys, that thread had managed to pass me by, sorry for the slight repetition.
The comments on gait analysis are interesting, it's not something I have ever considered, I tend to just get on with the running side of things. I have no idea whether I over or under pronate, but the Salomons seem to suit.
Even if I dismiss the gait analysis I am still looking for any recommendations on good shops in the London/Essex area.