Our 2 male GPs (brothers, 1 year old) are inside at night (in a 4'x2' cage in the dining room).
They are on fleece-easy to wash- and Catsan underneath because they are a bit 'fragrant'. Catsan doesn't stick to the fleece. I've got Megazorb in their outside pighouse but it sticks like Billyo.
I saw a silicone bead catlitter in Sainsbo (I think Bob Martins) and by the looks of it, it's made from smooth pellets.
The big advantage is, it only needs changed monthly. The GPs pooh on the fleece (changed daily) and at the moment a big (£9) bag of Catsan does 2-3 trays and last about 5-7 days.It has made a huge difference to the niff 
Pets at Home had a special offer on their own litter (wood pellets) but i worry about my washing machine as I can't get hay and grass off fleeces easily.
They aren't mentally scarred by cat litter either. GP1 has a pink Tatty Teddy fleece. And he's cool with it.
They don't come in physical contact with the catlitter because of the fleece.