We are unable to advise if further tax is payable on the gains.
As the gain is over £10000, you will need to submit a tax return for the tax year to date of death of your mother. Only then will be able to advise if more tax is payable on the chargeable event gain. You can see a helpsheet for gains on UK life insurance policies here:
HS320 Gains on UK life insurance policies (2023)