Hi Alex
Its mainly due to the future prospects. It appears there are far more opportunities in SE England for fixed wing ATPL pilots, as well as the pay in general being better.
I didnt mind switching as I generally enjoy aviation as a whole and want to be able to earn well from it also.
Its also nice that fixed wing is alot cheaper!
Each to their own though. After doing a few heli lessons I have great respect for heli pilots.