That's gonna be very tight, as the back seats of the V40 are moved towards the centre of the car. Further, even if you find one, I suspect it's gonna be unstable. I therefore plan to locate my booster behind the passenger seat.
As long as the seat will fit between the 2 belt clips it won't be any less stable than being on either side. I rarely travel with passengers, mainly short trips at weekends with the family, and when I do there is often 5 of us.