my mate is a sub contractor for all four of the recovery companies and he rates britannia rescue as the best, with aa and greenflag next and rac the worst
what he says is anything out the ordinary in any way will be bumped to contractors to recover to cut their insurance risks. boy racer cars, anything modified, most things with trailers etc
personally i used britannia for over 15 years with no issue the twice i have used them they appeared in about 20 mins
i am now with the AA as they were cheaper to cover the whole family fleet of four cars, haven't used them yet though, but sardass on here used them recently and sat for hours on the or near the m74, sure he will explain!