FIRPTA and UK Capital Gains - where do I pay tax

I recently sold a short term holiday let in Florida and had 15% of the gross sale price (before any deductions, so this is not 15% of profit) withheld under the USA's FIRPTA regulations. I need to pay capital gains tax but I am unsure whether I should pay in the UK and claim it back from the withheld FIRPTA in my US tax return, or if I should pay in the US and offset against my UK capital gains tax return.

Hi,
Under Article 13(1) of the UK/USA Double Taxation Convention, the USA has primary taxing rights on the capital gain you incurred on the sale of your property. The UK has secondary taxing rights. You would therefore need to initially report the gain on your US tax return to determine the amount of US Capital Gains Tax chargeable. The 15% withheld by the US is then used to offset your Capital Gains Tax liability there, with your retaining the right to claim back any proportion that proves excessive. You would then also declare the gain on your UK tax return and claim credit for the US tax charged to offset your UK Capital Gains Tax liability. This is available under Article 24(4)(a) of the UK/US double taxation agreement.
Uk/USA Double Taxation Agreement - 2002
Thank you