I have recently fitted head studs. And put on new head gasket.

I have gotten oil in oil in my water. Most likely cause is the head gasket, but the point of the studs was to make this less likely.

Can anyone think of a different cause?

Not 100% but on a previous golf gt tdi it was an oil cooler issue. Get that checked. Part cost was about £65 and change oil, coolant while being done..

Edited 25 February, 201412 yr by Cally77

if it was OK before hand and now leaking I would suspect the head gasket isn't fitted correctly....