Hmm, I was going to suggest grabbing the demo, but it seems to be gone from the file archive. I just tried it though yep, and it runs fine.

I'd be happy to share my copy of the demo but Craig or ED would have to comment on that. Maybe there's a reason it's not available any more.
If you plan to purchase from the Payback page on gp2x.co.uk, be aware that the site seems abandoned. Suggest going direct to Craig.