Hey all just wanted to say thanks for all your help, this is the set up I have gone with for now.
Set of 19x8.5 Work Emotion T7Rs. Wrapped in 245/35/19 tyres.
It has required rolling the guards, especially because the lip on the inside of the guards is about 20mm.
The wheels are a +45 ET so that required 25mm high centric Spacers to clear everything, with the height that I have the car, there is about 3mm clearance in the rear. So I'm glad my math checked out.
I would have preferred maybe 18in wheels and ran a 245/40/18 tyre to have a bit more sidewall, but these came up very cheap so I'm still super happy with the set up and this is more than enough allowance to do the XC90 brake kit now.
Once the handling is complete I can continue with the Audi 1.8t 20v /, RX8 6sp manual conversion that is sitting on the engine stand.