Sounds like a good plan with the litter tray.
I've never used Tesco P Food but I imagine it can't be too bad, have a look at the ingredients.
At first carry on feeding the same food as has been fed, I wouldn't change for at least 2 weeks & then gradually mix in the new food until she is only eating the new food.
Your cat (Izzy) will have a lot of new things to cope with so it's best to try & keep the food & litter the same as she is used to until she settles in.
Good luck I'm getting quite excited for you!
