Volvo XC60 - which high back booster?

[Bollockstothis101]

DD is 3 and needs to move into a high back booster. I ordered the Maxi Cosi Rodifix and went to collect it today. The sales assistant in Halfords said it doesn't fit properly because the car's rear headrest is too far forward and pushes the HBB forward when it's extended. The car's headrest can't be raised or removed. Has anyone found a HBB that fits nicely up against the car headrest without being pushed away from the seat leaving a gap?

Try this?

www.volvoxc.com/forums/showthread.php?16571-Headrest-removal-for-car-seat-installation&s=5a8eaedb58bf73f94b24b7c27be1cf0f&p=131543#post131543

The problem with getting a shorter HBB is that when your child gets taller, the seat will no longer fit them! You're supposed to use a booster until 135cm which will be quite a long time - my 9 year old has only just reached it this last summer.

If no luck removing headrest, what about putting the child in the middle seat?