There seems to be a real gap in the market for suspension specialists in the UK.
BG are the only one's I've heard of on a regular basis, but they must be out there. I imagine they are more for motorsport applications, and the labour costs etc will reflect their expertise. Enough to put off the average chav in a mk2.I suppose but I just tried to search for a suspension specialist in the UK and there is none (that I could find).
As you say though - probably down to demand. I imagine there have been businesses in this area in the past in the UK that have failed. I bet I could find a specialist pretty easily in Germany though.
average chav in a mk2.
Gould Engineering have been know to do Sachs, for considerably less than BG.
I like them purely as they have drawn their location map in paint: