With a clay tiled roof of that age, a surveyors report will always say its reaching the end of its life and needs replacing. The reality is that unless the roof leaks or lots of tiles are starting to crack, then the roof has still got plenty of years left in it.
Torching falling off is normal for a roof of that age, and as there is no felt or membrane there will be light gaps. Our 100 year old+ roof is exactly the same and doesn't leak. The surveyors report on our house when it was sold in the early 80s said the roof was at the end of its life. The surveyors report when we bought the house in 2010 said that the roof was at the end of its life. Twelve years later i've not had to replace one tile, it doesn't leak, and when we had an extension a few years ago that was joined into the old roof, the roofer's opinion was that it was good for another 20 years+.