cat litter

Bob Martins litter freshener in a tub that you sprinkle on top of the litter helps but is not 100%.
If your not actually using the sitting room for the duration can you leave a window open just enough for fresh air.

Apart from regular changing I think it's a grin and bare it situation

I use a mixture of cat litter- the type that keeps the poo etc fragrant and then I sprinkle a copious amount of the litter that leaves solids. I remove the solids x2 a day and I do not notice a whiff when I enter the bedroom that this tray is in. It does have a hood which may help. Tara is inclined to spray the litter everywhere when she is trying to hide her mess, hence the hood to contain the litter in the tray.

I have been using the wood pellet type recently and find that as long as I remove the poos as soon as possible there is no smell. It also seems to remain dry much longer.

I used to use the wood pellet type which I found had a nice fresh smell of pine. The problem was that when it got wet the pellets would disintegrate into sawdust which the cats would walk all over the carpet.

I second that Deedaa

My old cats had to use litter trays instead of going outside and I used the clumping sort. I think as long as you take out the clumps of wet or soiled stuff a.s.a.p., you should not get residual smells. Maybe you have an oil burner and could use some lemon grass oils to burn?
If the dog is not with you too long, could the cat not stay in the utility room with some comfy bedding? (although that seems a bit mean of me!)
My present cat is stretched out happily on the sofa at the moment. On second thoughts, I think you are right about location - cats do like the best seats in the sitting room, don't they!

Dog might be with us for a couple of monthhs, hence the complications. Cat needs to be comfortable but I am not prepared to give up my sitting room! The things we do for our children

I agree about the wood pellet type: nice smell but gets everywhere. I use Biocatolet, which is paper pellets, and find it good at disguising the smell and it doesn't get round the house so much. There are other paper types but they are not half so good.

I've got an Ashleigh and Burwood fragrance lamp that gets rid of any bad odours and is supposed to purify the air as well. They're not cheap but they're very effective. I wouldn't change your cats litter in any way; they don't like change. Could you put it in something like, say a dog crate and cover it up; also perhaps use a dap diffuser in the room so the cat doesn't get stressed by the change in routine?

ever clean litter
I use this clumping litter, usually the scented variety. It clumps really well so that the wee and poo can be scooped out using a fine scoop. The remaining litter only gets changed every few months, apart from the odd top up, as there is no odour left. It seems expensive, but works out cheaper that way. I do have a litter tray with a roof to avoid spills. Hope all goes well for you.

fine scoop