Well that was a major faff.. changing the battery, a 5 minute job, right?
2 hours later, finally done!
Battery clamp bolt spinning but not releasing, tried to take the battery tray out, the last bolt is of course UNDER the battery, plan B, drill bolt head off and knock rest out with a FBH, reassemble with a nut n bolt.
And the new battery doesn't completely fit properly, I'll need to 'modify' the tray slightly when I have more time so it slots in properly.
Character building isn't it!