ND are pretty good about that, you can probably get them to confirm the work they did from just the rego; obviously if the engine has been transplanted it's harder, but they will have stamped the block so it can still be traced. - That's entirely possible because if you'd spent £4000 with Mr Norris on an engine and clutch etc, why would you not have the ND intercooler too (which are quite good)?
I'd guess that he doesn't really want to sell it, but can't justify the cost of a new turbo... and now it's been sitting too long and doesn't want to start. Perhaps he has now lost interest in it, but I'd want to see it start and listen to the engine to be sure it is the turbo that's let go and not a piston (or ring).
If you looked at it as the purchase of a forged engine with a free rolling shell, then it's probably quite a good deal and you could go on to build a good car from it... but I'm guessing that if you don't want to put much work into it, this isn't the car for you.
Anyway, I don't know who's that is; sorry.