i have just got a cream irish wolfhound, but on his back is quite a thick covering of grey hair , can any one tell me when or if this will go. He is 14 weeks old.

Hi there, if it is a solid wheaten pup, has it got black points, ie muzzle ears and black/grey at the top of its tail? If it is a solid wheaten, the grey on its back will go at about 6 months of age.
If it has ANY brindling on it at all, the grey will probably stay and spread all over. Hope this helps a bit.