I use Morrisons wood pellet cat litter, a bit cheaper that the PaH version, though once we've sorted out the shed I intend to buy the giant bags of wood litter pellets as they are more cost effective.
I only use the litter in Ben's litter trays, not anywhere else. thats straw or sawdust.
I admit that Ben uses the cat's litter tray, when hopping about the house! (He has his own, but shares with Evie for some reason, litter tray, water, feeding zone, toys, hiding places, hugs. Very odd but cute) And that has Catsan Hygenic litter in it, and does him no harm!