Re: new clutch slips when hot fine when cold!
just because you have a bill for a full clutch doesn't always mean that was what has been fitted.
Other things I have seen are people using a little bit of glue to stick the plate to the flywheel when they dont have access to a clutch aligning tool, once the clutch is engaged it breaks the seal and works fine.
Only problem is if you use to much or the wrong type then when it gets warm it gets sticky again, when cold it is in its hardened state.
The only other thing I can think of is a faulty oil seal in the box that, when warm, expands and leaks a little oil onto the plate causing the slip, but would think this to be fairly unlikely.