you can get a kit from mad-for-it on ebay for about 150 notes however i would fit a set of 4 taper plugs into the front oil returns as i dont personally like the idea of relying on the head gasket to blank of the oil return galleys as the gasket can deteriate and break down overtime.
also the decompression plates are about 29 quid from the same mad-for-it performance
and from my own experience i can say that a 1.8 zvh running std everything apart from an exhaust and chip to allow 1 bar of boost should give a return of about 180 bhp at the fly and 145 at the wheels.

and that engine came out of a skip with so much piston slap you would think the bottom end was knocking
another mate of mine got 195bhp@flywheel out of his with the same set up but inc. a home done flowed head and kent cam