I finally went and got myself an adapter. It ranges from 3 to 12V with 1.5A capability at 3V and at the moment I am using 6V. For those in the future who need this info, use 6V DC, negative tip polarity.

However I am now getting interference in the picture which I didn't get with batteries. I have tried 4.5V, 6V and 9V but no change. It is a wavy sort of distortion which shows most on a black background.

Any ideas? Or just cheap chinese production methods?