Hi Beverly,
Archived exchange rates can be found at
Exchange rates.
As the disposal took place at the end of April 2023, this is the 2023 to 2024 tax year, any gains that you need to declare, will be in the 23/24 tax return, in the SA106 (foreign) and SA108 (capital gains) pages, which will become available after 5 April 2024.
Private residence relief is calculated as the number of months the property was your main residence, plus an extra 9 months over the number of months you owned the property. (147+9)/163 times the gain. The resulting figures from this calculation are deducted from the gain. As the property is jointly owned, you will only declare your 50% share of the property.
Thank you.