It looks like an 029 would fit:

http://www.ebay.co.uk/itm/S4-029-Bo...29-/192039326882?_trksid=p2385738.m2548.l4275
but not sure which way the terminals are.

Cheers, that would certainly do the job.
I'll look up some reviews on it

I'm still tempted by this for the cold weather:
http://www.ebay.co.uk/itm/1x-Exide-...487451&hash=item2ca7b6fd0e:g:8BgAAOSwqrtWp18g

But I think I'm being pedantic.

I see what you mean about trimming off the "feet", could you modify the frame slightly? Mine unbolted from the tray.

As far as I can tell, the outer battery brackets and the air filter are attached to each other so I'll have to have a think.
I'm a stickler for keeping things original which is also a major problem, haha!

I've had two, consecutive, batteries on the wood blocks now without trouble, so perhaps I can live with it not fitting.
It's secured with a strap across the middle which seems to keep it in check too.

I think I'll experiment with the old battery which is 1.5cm too long and cut the feet off and see what happens.

Cheers, Rob!