Another XC90 owner here until 3 moths ago when it went in for an XC60. Had it for 26mths.
Most XC90’s are/have been second cars, kids seats in the back and normally serviced on time. Stretch to £15k and you’ll get a decent SE (I got £16k PX on mine) and if I were you steer clear of the R Design as it runs on lower profile tyres/bigger wheels and the ride is chalk and cheese away from the SE.
As for interiors, well mine was only used by us two most of the time, great for swallowing bikes/boards and occasional towing. The rear folding seats were ace and easy, 30 second job. The baby seats in the back fold out easy, I did mine a couple of times a year or so ago and I recall it being easy too.
Great for ride height, hop In/On rather than hunker down and in, if you get my drift. Easy to park despite the size of the thing as they are slim and overhangs not a problem if you’ve been used to a V70. Mine had the rear camera and side warning thingy camera in the mirror which was great for parking alongside kerbs. Its an option so try to seek one out. Sat Nav, mine didn’t have it as Std so I used a Garmin stuck to the dash in the middle, fine no problems at all.
Thirsty buggers though. 25-35 was about all I got. Occasionally I’d hit 40 but that was just the optimistic nature of the on board computer. As was it wasn’t an issue for me and I’d get roughly 500 miles out of a tank if I took it easy, 350-430 more often than not.
Nothing went wrong, trouble free, Volvo serviced and a blinking great car.
Sold for an XC60 SE as I wanted a smaller car and decided 7 seats were too much for me and not required. I could add more about the 60′ but it’s only got 5 seats, so no point.