As I just put in another thread, after reading 'Kat600's' comments with a similar prob, I stripped it down for a fourth (or so) time and checked the seal on the slave piston VERY carefully.... There is the tiniest leak, not enough to see fluid drip out but just enough to stop the system pressurising fully when the lever is pulled. I'm hoping this is my problem. Have ordered a new seal kit and am looking into investing in a billet housing. Better quality than the original, looks nicer and also negates the need for the slave cyl support bracket. Thanks for everyone's advice.