Hi, we're off to the UK in June, and will have three kids in car seats. DD1 and DS are in boosters, so we have two collapsible boosters that don't need a top tether that we will take for them. We were planning on hiring a car seat for DD2, who is still rearfacing, but its going to be about $300 to hire one (which is ridiculous, since we just bought one for $115!!!) anyway, we're thinking we are going to take the one we just bought. I know in the UK it is either a seatbelt only that fastens the seats in, or isofix. Can we take ours with a top tether? Do we just not use the top tether?