Thought it worth posting this as I have done a lot of research and couldn’t find any up to date info when I was researching this. Obviously this worked for us and might not for other makes of cars. Mothercare allow you to drive up and test the car seats before driving and there is the in car safety centre in Essex which will also assist.
We have a BMW Touring (5 series) and didn’t want to change the car to a MPV.
We have got the following into the car:
Pebble (belted no base) behind driver seat
Britax Eclipse (belted) in middle seat
Britax Advansafix IV R (isofixed in)
Followed by when baby has to move to next seat up
Britax Eclipse
Maxi Cosi Rodifix AP (belted)
Britax Advansafix IV R
Seats do touch but according to Mothercare this is ok. There are differing views on this as Halfords will say they shouldn’t touch. Up to you to make your own decision according to your own specific needs obviously.