Hi again,
a grand would easily cover the cost of a head overhaul providing you do the work yourself or with the help of your mate. Go for a decent head gasket set though and a good set of head bolts. Get the valve guides machined for inserts and get the seats recut at the same time, any good machine shop worth their salt will do this as part of the job.
If you need valves be sure to get original spec, there are a lot of cheapies out there but are not really suitable for high performance turbo applications, this is especially important on the exhaust valves where sodium filled are used.
Woodford Garage Motorsport are very good for parts, I dont ever use anybody else as they are keen with prices and always forthcoming with help and advise.

Regards, Mike.