I used Northway in Edgware/Colindale, I realise it is a little out of Herts, but I live in Watford.
I tried 3 different companies in Watford to set up my M5, and none of them could get it right... took it to Northway in Colindale, they spent over 2 hours on it and set it up perfectly.... have recommended many other to them who have all returned happy.
I got Fairway in Ricky to set it up, then went to Northway same day to find the cambers were miles out!!!