So just advise please , My SantaCruz carbon frame and Raceface post.

Ive messaged Stiff , Jungle and looked on various forums for seat clamp torque specs with the hope clamp

Ive had 3.5 with grip paste , 4-4.5 without , and website states torque to clamp specs (so thats 8nm with Hope ) needless to say ive not gone to 8 yet i stopped at 5.5 and the post dropped a little under my measly 13.8 stone.. Obviously I really wont be over tightening the clamp, anyone have any further info or advise

Why did you only use grip paste @ 3.5?

No Stiff said 3.5 with Grip , Jungle recommended 4-4.5 with grip and it still moved.

Ive stripped and re cleaned this evening with ISA and lashings of grip and torqued to 5nm in a vein hope that this solves the problem

If you use a really thick layer of paste then the paste will flow, so keep it sensible. You can use grip paste at any torque setting so no reason to leave it out.

Is the frame a particularly loose fit on the seat post?

Could try rotating the seatclamp 180 degress so that it clamps the seattube slot differently

Went to town last night with the paste and doesn’t seemed to have moved from the commute. My thoughts are with the Hope clamp as apposed to the Santa clamp that came with the bike.. Lets see what happens on the ride later