We get our cat litter from Pets at home, most of the wood pellets type is about £11.50 ish for 30 litres
They used to have a really good one in a blue bag called something paws but don't sell it anymore.
In our quest have been trying different brands. Last time got the one pictured below and wow its totally full of sawdust, We had just under half a bag left and I've just sieved 3 strawberry punnet ( 400g size) of sawdust out of it.
So heads up , don't waste your money on this one .