A Q7 is approximately 10cm bigger all round than the cars you mention above, which is quite a lot on an already very large car.
I looked at a Q7 a few years ago, and I think it really is too big for British roads and car parks.
Ten or so years ago I had an XJR, the aluminium bodied one (previous to the current version), and that was the largest standard car on the British market at the time (excluding something like a RR Phantom), being bigger than an S-Class.
Frankly I thought it was just too big - multi-stories were an absolute chore - it was barely possible to get parked in one, and getting out frequently required ridiculous contortions. Spaces in most car parks are just too narrow for these very large cars.