I am visiting home for Christmas with twins who will be about 15kg. We can't bring their own seats as they are Canadian ones and therefore not legal in the UK. Weight wise they could go into a cheap high backed booster but I think safety wise they still need a five point harness. The options are to rent a seat which is ok for them now or to buy one that could be used for future trips too and stored at the grandparents - my sister is in a similar situation so it would be used occasionally. If we bought we would go for a group 1-3 seat so it could be used for the longest period. What would you do? I don't want to spend a fortune but want them to be safe and I know you can get a cheap 1-3 seat from Halfords but feel it can't be very good (if someone knows it is please let me know as that would be great!).