I can recommend AforAlfa (
http://www.aforalfa.co.uk/ ) - 01296 415712 or 07745 233472 - he is based in Aylesbury but is mobile and he came to me in High Wycombe.
Paul did my cambelt (etc) and a service last week in the rain on my driveway (fortunately he had a canopy with him!). Very professional, nice manner about him and he did the job for a very good price.
Would recommend.
