Not exactly. And let's call it a Buyers fee, not Indemnity fee (see 8.4 in my post above):
No Buyers fee: Buy for £10000, sell for £12000, pay VAT on £2000 margin.
With Buyers fee: Buy for £10000, add £300 buyers fee, sell for £12000, pay VAT on £1700 margin. The lower margin to pay VAT on gives you your saving.