I agree, it was a Which! best buy 2 years ago. You could get it as Isofix or seatbelt. It also fits in most cars, we have a Ford and it fitted brilliantly.
Get Halfords to fit it first, Babies R Us were useless at fitting both the ones we have bought, we wasted 2 trips to the store. Ended up buying the next stage one at Halfords and they matched the price from BRU when we asked.