There's different options:
- Mortgage protection cover, this decreases in line with your mortgage balance so is the cheapest option. This at a minimum will satisfy the bank.
- Life cover will be for a fixed amount. This does not decrease in line with your mortgage and you could choose to continue the cover after you have paid off your mortgage. This will also satisfy the bank but will be more expensive. If you are relatively young though the premiums will be cheap and this can be a cost effective way to cover both your mortgage and get life cover. If the worst happened and in 5 years you passed away, the 100k would be used to clear the mortgage balance with the remainder going to your estate.
- Mortgage Payment Protection cover. This is something completely different which can be taken out to pay your monthly mortgage repayment if you cannot work due to involuntary redunandancy or illness. This is quite expensive and is probably not what the bank are looking for. I mention it in case they try to push this on to you - there is no legal requirement for this type of policy.