Thanks for the reply, that is basically what was done, He took it to a good machine shop local to me. and 24 hrs later and a bill for £180 (which we thought was OK) he got it back with 6 empty heater plug holes! The shop had to make up a special tool/puller to remove them. The panic came from the first so called 'machine shop' if it had'nt gone there first, there would have been much less drama!
A possible reason was the last set of plugs had been put in and not tightened enough which had allowed a build up of carbon on the threads and seat, But who knows....
The carbon may have been caused by a faulty egr valve
which was disconncted a few weeks ago
At least he is a bit happier now