Thanks. When you say "It's quite normal", do you mean to refuse a
mortgage because of no felt?

It is usual to have no felt. Indeed, it is unusual for a Victorian/Edwardian
house to have felt, unless it has been reroofed in the last few decades.
There is no problem with mortgages.

If you decide to reroof (it isn't necessary just on the basis of felt) then
ensure that a high quality breathable membrane is used. This gives much
greater flexibility when it comes to insulating the roof.

Christian.