I have use acrylic repair gunge, you get a year or two in exposed locations.
My new flat roofs are both EPDM rubbery material which seems to be OK so far. It was installed by a good contractor with correct slope and no pooling.
Wasn't this mob was it?Thanks. That would be the ideal solution, but unfortunately it didn't. The company that did the work has since changed hands, and we have nothing on paper, so I suspect DIY is realistically our only option.