Not worth rebuilding an engine on a car this old. Can get a low mileage for just over £200. Rings gaskets plus any machine shop work will come to well over this.
The car is only worth £700 so may even scrap it.
Seem like I was too quick to assume the engine had low compression. Just done a test and it's fine, high compression over all the cylinders.
The starting problem I had was after the battery had been disconnected so I'm wondering if it's something to so with the standard map if the ECU.
I managed to start the car by squirting some oil into the cylinders to give it greater compression. Once it started it ran rough and wouldn't tic over, but settled down after a while. Took it for a good test run and now it seems back to normal, with easy starting when cold.