clutch problem freelander td4

Hi all, bought my freelander a few days ago its a td4 04 plate. having problem with the clutch. It goes in to gear fine and the biting point is fine near the top. Sometimes when i accelerate hard the clutch is slipping and carrys on doing it. sometimes it doesnt do it at all. its mostly when going uphill its just revving but not reli going anywhere.
Anuyone have this problem before or know what it is? any help appreciated thanks.

Problem sorted now it must have been because might have been stood for a while before i bought it or something. after a a long drive doesnt seem to be doing it anymore.

if it starts again and you have to have a clutch done get the master and the slave done at the same time