I had my clutch redone by a specialist Jim Berry at Race Clutch, he did Aussie RS500's and could quote all the required pressures and comparative specs on cosworth and other clutches. I suggest you call Jim even though he is in Australia It would be worth it. You might find another guy like him in the UK.
His number is +61738479999, mobile +61419727623, remember to allow for the time zone difference, I think you would ring him early in the morning.