Hi,
To calculate any gain, you will need to convert all values from the foreign currency to GBP sterling using a just a reasonable exchange rate at the time of acquiation and disposal.
Under the terms of Self Assessment, we do 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. For your convenience, there are exchange rates at
Exchange rates from HMRC in CSV and XML format
and for older rates at
Exchange rates Foreign exchange rates and spot rates: 1 January 1989 to 31 March 2009.
You are free to use any of the supplied rates or one of your own choosing.
You advise this property was your main residence, you may have private residence relief available to reduce or cancel out any gain.
Have a look at
HS283 Private Residence Relief (2024), as you may have private residence relief to reduce or cancel out an gain that arises.
There is a calulator at
Tax when you sell your home to help you work out your gain.
You will need to report the porperty disposal in a self assessment tax return.
Thank you.