If it's just rattling try a set of cams and a set of tappets - cams are about £150 each for any BD 8,10, 12, 14 AND ON.... and Matt lewis will do a set of OE followers for £80

Check all the cam carrier studs are still tight in the head as i have just had to helicoil 2

If you go for a rebuilt head your looking at £30 each for a valve and £7 each for a guide going by burton prices - then a head gasket set is going to cost between £120 - £250

So roughtly costing £1110 if you go for the complete thing