Something that seems missing from this thread is the fact that there's been a new exam venue in use for the past few months, LGU/London Met Uni, at their Tower Hill campus in central London, which was a solution to the outrage of LMU students regularly being sent on a trip to Silsoe or even Glasgow when the Gatwick venue was oversubscribed.
Don't see why the CAA wouldn't agree to provide exams at venues in the south-west and the north-west aswell if flight schools ask them hard enough?