Cheers guys - battery out, had to modify the base of it so it would sit properly in the tray, then filed the insides of the terminal clamps so they were shiney and rough, did the same to the battery terminal posts, then widened the gap on each terminal clamp so when I re-tightened them, they closed better around the terminal posts. Gave them both a good dollop of copper grease and put it all back together. So, the battery is now sat firmly in the tray, which it wasn't before, and the teriminals are rock solid on the posts - out for a drive in a mo so will see.
No lighty, me likey - good times!!