This is probably academic, but it used to be the case that if you had owned the vehicle for a year or more in the overseas location, and you kept the car in the UK for 2 more years (or re-exported it), then you could import it duty-free.
I did this back in the late '70s with a Datsun 260Z, which cost 'peanuts' (compared with the UK list price) in Dubai (I was actually living in Ras Al Khaimah) and the shipping costs to the UK were very low (In those days, loads of ships were arriving in the UAE full of general cargo but returning to UK with very little, so the shipping Cos. were pleased to bring back anything they could get their hands on).
It doesn't sound as though your situation would benefit from this, unless you 'come and go' over more than a year, buy a C7 on your first visit, and store it for a year.
Another factor (then) was that the used-car market was virtually non-existent; everyone was buying new cars, so rather than 'giving away' a
nice machine, it made sense to ship it back to the UK. Is it still like that now?
Good luck with your Corvette hunt, whatever you do!
J.C. (1911)