Thank you for the reply, I have since removed my cylinder head and had the valve seats replaced. Fortunately I do some outwork (lathe machining such as replacement small-end bearings) machining for my local machine-shop and was able to work off the cost.
I did find out that the combustion chamber is machined directly in the head and it would be impossible to skim a low compression head into a high compression one, so the low compression head I bought has gone in the scrap bin.
I am now going to investigate fitting a Weber Carburettor, I think I read somewhere that a 34 ICH will fit and do a much better job than the Zeneth fitted.
Regards, Terry