The surveyor reckons it needs more down pipes at the back and front.
I've had several experienced roofers recommend 1 or 2 more either side.
I had a young lad come around ask me quite sensibly have you had any overflow problems? I've only just bought the place, but the answer, to my knowledge, going by the ceilings, is no. He reckons if there's no problem, no need for additional down pipes.
Be interested to know what anyone thinks?