The 1150 two stud heads are easier to get the studs out. The three stud heads are a bastard.
Just removed two 1150RT heads ( 1150 RT's have three studs) and had them machined out and timeserts fitted. That's six studs, all for £70.
Worked out cheaper for me to pay the engineering shop than drill them out and fit the inserts myself.
Mine is in Woking. Mikeyboy has one as well, but not so old. Steptoe too. I can drop you details but he's the kind of fella that you need to deal with face to face rather than by post.