Unfortunately, we see this all too often...Bidding on a car, especially a RR/B without prior inspection, auction or in private hands. A thorough inspection by a competent shop or tech familiar with the marque would have saved you thousands....many thousands in fact. A Turbo Bentley is one of those cars, especially with no known history and high mileage that is likely prone to blown head gaskets.
Unfortunately, the cost to repair may equal or exceed the value of the car. It would be prudent to clean up the valves, check guide clearances, replace valve stem seals etc. when the top half of the block is torn down. There will be a painful amount of hours for this job.
We see so many cars literally dumped on auction sites as a last ditch attempt to get rid of them and let someone else deal with the aftermath.
I know you're sick to your stomach by now and my best advice going forward is have it done properly by a known firm that has performed this procedure. You do not want to go thru this again. Spend the money and do it right and listen to professional advice. When done you will have a car to enjoy and if treated properly will give you many years of pleasure.
1980 SWII LRL-41587C FInj
1976 SS LWB LRE-23114 Harkness RR