Just a rough but educated guess.
Assuming it's well lubricated, and the engine inhibited. I'd start at about £15k, subtract a LAME's best estimate for the cost of recommissioning the engine, re-assembling and doing a star-annual, incorporating all SBs and ADs for the last fifteen years and the CAA's fees for a new CofA.
Offhand, I'd guess that'll probably come out somewhere in the region £6-£9k.
G