Hi, for a recent engine survey I used Colin Ryan (excellent chap) who drew the samples from the engines and sent them off for analysis to the Oil Lab Ltd, 15 Limefield, Blackburn, Lancs, BB2 6PJ Tel # 01254 677101
Hope this helps
Mark
Its dead easy to take the sample yourself, Oillab will send you the bits you need if you send them some money.
Warm engine and suck it out of the dip stick hole!