Whenever I park my 51 plate Td4 facing downhill I seem to get a problem with the brakes. The brake pedal always seems very firm and the brakes are not very effective initially. Once I drive off and use the brakes a few times it returns to normal. Any ideas what's going on?

Hand brake sticking on a bit; such that you are effectively only using the front brakes.

Thats all I can think of. Easy to test my theory....leave it in gear on a downhill (without handbrake on) and see if that makes a difference. Point front wheels into the kerb if you are worried.