Life insurance payouts would normally be considered part of the estate and liable for inheritance tax.
Where was your father domiciled when he passed away?
If he was domiciled in the UK then the life insurance payout should have been added to the total estate.
He we was domiciled outside the UK then only assets that were in the UK at the time would be liable for inheritance tax.
As a UK tax resident, you are liable for capital gains on any investments around the world that you repatriate to the UK. That means you pay CGT on any gains since after you inherited it.
When you repatriate the money, the HMRC can ask how you got hold of the money. If they discover that you should have paid the inheritance tax, they will ask for that money plus interest.