EPDM roof

Beechnut
That sounds like the system we have on our conservatory roof.
I believe it's the same system that was used on the Olympic pool.
Not cheap, but worth every penny.

Thank you MerylStreep. I have seen it advertised quite a lot so I watched a YouTube video to see what it was exactly and it seems it is like a pond liner that is stuck down onto board.

My neighbour just replaced his conservatory roof with this roofing. He’s a tradesman so did it himself he said it was expensive but so far so good no leaking but I have noticed it’s bubbled in a few places but that might be his fault. I’m assuming there are companies who specialise.

We had our garage and an extension roof done in EPDM, in 2012.
So far, so good, and we were very pleased with what they did.
The chaps doing it were also replaced all our guttering, fascias and soffits. The total bill was just over £4000 for all the work.

(One of them came back later in the year and replaced our shed roof.)

Thank you tanith and Auntieflo.