Is the wood-based litter like Feline Pine? If so, it's probably exactly like the small animal version. But you might be able to find cheaper stuff that's just as good at a feed store or horse supply store. I don't know how available it is in the UK, but some places sell wood pellet bedding for horse stalls and it's usually only $5 for a huge bag, where pet stores sell a tiny bag for $10+. I love this stuff!
Bilbo- could you print off some info on clumping cat litter and rabbits and bring it in to the PAH?