Hi
As a UK resident, you are required to declare your worldwide income and capital gains.
You should therefore report any capital gain arising from the redemption of the Indian mutual funds in the Capital Gains pages (SA 108) of your Self Assessment tax return, and claim any Foreign Tax Credit Relief due in the Foreign pages (SA106) under the heading 'Capital gains – Foreign Tax Credit Relief and Special Withholding Tax'.
HS261 Foreign Tax Credit Relief: Capital Gains (2018)