If you are having problems with fluid temperature go for the CL Brakes super dot 4 race brake fluid as it has the highest dry boiling point of all the ones we've seen
another worthy mention is the Castrol SRF which has a slightly lower dry boiling point but a marginally higher wet boiling point. As its for hill climbs I would imagine dry boiling point is more key as probably change the fluid enough for the wet boiling point to not really come into effect..
All sorted now the car goes in on Monday for a cam belt and then the brake up grade when all the bits arrive hopefully later next week. Thanks for all your help