Uk - would you buy a group 1 car seat or a group 1,2,3 and why please? Thanks?

I'm in the Netherlands, but we have the same car seat classifications.

I put my oldest in a group 1 car seat. When my youngest (they are close together in age) outgrew his group 0+ car seat, I decided to buy a group 1,2 (a bit less common than 1,2,3) seat for my oldest, and use his old seat for my youngest.

When I saw the differences, I was happy with the decision to put both kids in a group 1 seat when they had just outgrown their group 0+ seat. In comparison the bigger group 1,2 seat looks less safe for a baby/young toddler around a year old. Sure, the straps adjust and there is a kind of insert to accommodate younger children, but it'll never be as snug as a group 1 seat. I particularly see that the group 1,2 seat offers less protection in case of side impact than the group 1 seat. There will always be some concessions in the design when it has to fit children of a bigger age range.

By the way, are you aware that these days good group 1 seats suitable for rear facing are becoming available? This is because of recently changed EU guidelines. These seats became available JUST too late for my kids, but I would really recommend looking into it. Rear facing until at least 2 years instead of 1 year really is much much safer. I know Maxi-Cosi now has rear facing group 1 seats, and by now there are probably more brands following the new guidelines.

It's just a personal preference hun. I would personally buy a group 1,2,3 to start with because it will save you in the long run. :)