Oil Leak

I had the head gasket done about 6 months ago, but oil was leaking for several weeks after. the garage changed the cam shaft seals twice! still no joy. Then they sent the car back to the company who did the head skimming for them. The leak stopped until yesteday. Now it's back. Someone mentioned that the sealant under the camshaft carriers is of a special type. (the camshaft carriers need removing to skim the head). I'm wondering if they've cut corners to save money. Any ideas please.

take it back, demand a courtesy car while it is being fixed, and if they dont play ball, say if it aint fixed you will be contacting trading standards and demanding compensation as well.