You could probably do it cheaper(DIY ), but it depends on the state of the ancillary parts. If I were rebuilding I'd also be using new oil and water pumps etc. I would have thought his discount would help alot though. Get the company who has quoted to list everything they intend to do/replace for the £3K assuming a straight forward rebuild. This will only be ballpark though as you never know what you'll find when it comes apart. Also is the £3k drive in-drive out?

What is wrong with it to suggest it needs a rebuild anyway, who diagnosed it?. How many miles has it done and has it been maintained properly?, as a stage 1 engine shouldn't get all that stressed.

I think Grove are in essex and have a good rep. Or he could go further north, up to SCS at peterborough, or west london to MA Developments in maidenhead.

Gt him to ring around an get some other quotes

Edied to say, I've just seen Rob from SCC is on here now, so there's another garage to take it to who will give a no-bull, top service. I hope the cheque is in the post Rob