Chappers, I'm not aware of the recent law change you refer to. My understanding is that you would need to repay a twentieth of the VAT for each year short of 20 years that you held the property. On plus side, inflation doesn't apply to the sum you would need to repay after selling.

If you find any evidence that the VAT refund needn't be repaid (other than on Agents's sites) then please paste link on this thread.

Issue of sellability is a big one for me. Look carefully and you will find developments where purchasers can buy with leaseback or buy for their own personal use. It is more likely with these developments that you will not have to renew your lease further down the line. (That's an assumption, you should draw your own conclusions there.) If my assumption holds your property's resale market and value will not be restrained in the way that other leasebacks are.