You have probably done your homework, ,but, is it not cheaper to have the engines overhauled in the US and fly the thing over?
My point is that getting a dismantled airplane with time expired engines on the UK register will cost you an arm and a leg.
With engines done in the US and an Export CofA by a DER would make it a lot easier in your dealings with the CAA.
I tried the other method many years ago and it was very difficult and I had US and UK licences.
Good luck.