Yes, you may have Income Tax to pay on the gains arising from the surrendered policy, even if you transfer the remainder into another saving scheme. For UK policies, there will be a notional tax, equivalent to the basic rate, that may offset any further tax liability. If the gain is over £10000.00, you will need to report the gain in a Self Assessment Tax Return.
Have a look at HS320.
HS320 Gains on UK life insurance policies (2023)