If the sale is subject to UK law then transit risks reside with the shipper. So lawyer up.

And because wood is not a uniform extruded material, mass produced guitars all still sound different from each other. Buying unplayed is unpredictable unless you are particularly well up on the make (and I still managed to buy a really dud Hagstrom, once) and unless the price is more than 50% below retail (or second-hand retail as the case may be). I have 6 Hagstrom J-45s and all sound different.