OK, I assumed (shouldn't have - 'ass' out of 'u' and 'me') that, unlike scart plugs, a scart socket was a scart socket, they all having 20 holes.
I have now used the other socket and I have colour. Thing is the quality is still poor - substantially worse than a video cassette.
I'm pretty sure now this must be due to the signal degradation when converting from SVHS to scart - I'm surprised though that the loss in quality is so marked. If anyone is thinking of using a computer dvd drive to watch films on a TV, make sure your TV has a SVHS input!
Thanks to the both of you.
MH