If you have lost a loved one and there is a mortgage to pay, you should continue where possible to make the mortgage payment or contact the lender as soon as you are able to inform them of your loved ones death so you can make arrangements.
As your duty of an executor, (if applicable) and you are unsure of the mortgage lender, my first advice would be to check bank statements to see what direct debits are currently going out and call every provider.
They may be able to offer a payment holiday, interest only strategies or arrangement to pay, until you decide how to pay off the mortgage, which is usually by selling the property (difficult in the
current climate) claiming on any current life insurance policies, or taking over the mortgage payments until mortgage is repaid in full.
Failure to keep up repayments on the mortgage could mean it could affect your own ability to take over the mortgage, move it to another lender, and in extreme circumstances, repossession, although during the Corona Virus crisis, the FCA has urged all lenders to temporarily cease Repossession orders.