i bought a used maxi cosi for my nanny to use. she doesn't have isofix so will use it with the seatbelt. however it was given to me on the base and i can't get the bloody thing off! been wrestling with it for the best part of an hour. can anyone who owns one tell me: is it the grey button at the front that you press? there's also a grey plastic thing at the front of the seat and when i press that it slides backwards and forwards but doesn't come off. aargh!