I use Biddenden Motor Works in Dartford, they are very reasonable and know what they are doing - they can also set the geometry etc afterwards as that will more than likely need tweaking.
Depends on the car really and how easy/hard it is to get to everything I supppose to drop the old suspension out - best off ringing and asking for Martin (owner) or Paul (head tech) to ask for a cost - even its just for advice, their a friendly bunch.
Have you already bought the coilovers? I believe GAZ headquarters are in Essex and will install.
Burnt Mills, Basildon. They are really helpful and friendly - I took in my 35 year old Koni's and they built/supplied adjustable shocks to the same spec and dimensions.
