Hi David Male,
"Under the terms of Self Assessment, HMRC does not provide an official exchange rate and the onus is on the individual to use a just and reasonable exchange rate for each acquisition and disposal. None the less, HMRC does have an archive of exxhange rates, which you can use if you want to.
(
Exchange rates from HMRC in CSV and XML format &
Foreign exchange rates and spot rates: 1 January 1989 to 31 March 2009.)
There is a calculator at
Tax when you sell your home that will help you work out if there is a capital gains liability in the UK.
You will need to use a just and reasonable exchange rate, to work out the acquisition value and costs and convert to pounds sterling, using an exchange rate at that time.
If this property was your main residence at any time, you may be entitled to claim private residence relief, have a look at
HS283 Private Residence Relief (2023)
Any gains should be reported in a self assessment tax return on SA108 and if you paid capital gains tax in France, you should also declare on SA106, where you may be able to claim a foreign tax credit.
Thank you.