Yes, it is a pitched roof, and I am talking about the felt between the
rafters and roof tiles (concrete, I assume).

This is an old Victorian house so there is no attic space the top floor
has two bedrooms with obviously a ceiling above them, then rafters then
felt, then tiles. Absolutely, no attic space at all.

The ceiling was looking very old and tired, so I removed it to renew. I
definitely did not cause damage to the felt by removing the old
ceiling.

The leaks were only slight, but it was obvious that the felt was in bad
condition with holes and feeling very brittle.

I am about the add to my mortgage to do some improvements around the
house and am looking at the need to budget for the roof.

Or I could just move, I suppose!