Help with booster seat confusion!

[whoami24601]

My small DS (16.8kg and nearly 6!) is ready to move into a booster. I've got a Citroen C4 grand Picasso but often need three car seats in the back (1 other booster and one RF baby seat). I took him to Halfords but the ones there all seemed really wide and wasn't sure they'd fit! So I'm looking for a slim HBB with good side impact protection. Budget is up to £100 so nothing crazy! Can anyone advise?

Oh forgot to say isofix would be a bonus!

Anyone at all?

We had a britax adventure which at the time seemed among the slimmer ones. It wasn't isofix, but they may do a similar one which does.

If you need to get three car seats on the back seat, I’d suggest not getting isofix. We have found that our car seat, which uses isofix, wastes a lot of space next to the car door, meaning the person who sits in the middle seat ends up being squashed up to the third person.

We have the joie trilo with isofix which DS says is very comfy. I k ow friends like the cybex HBB

It might be worth having a look at i-size boosters as they are generally narrower than others.

I did look at the joie trillo a while ago and it seemed good. I find choosing a car seat so stressful. I want them to be safe, but some are crazy money and I have no idea why! What's so much better about the £150 ones?!