We had a collapsed drain in the car park a few years ago, every few weeks it would back up, I used a company called Metro Rod, they blew a polythene tube down the pipe and then pumped in fibreglass, then pumped hot water through to cure it, it was about 30 metres long and took them about half a day, from memory it wasn't stupidly expensive, and fixed the problem, obviously it reduced the size of the pipe a little but it wasn't an issue, it was in Essex
I should add they did send a camera down first