On switching to the 4GC, I had to replace my 7 yr old daughters seat, with one with an isofix mount to stop it sliding over the seat belt clip.
One trip to Halfrauds later, £90 on a Britax Romer SL and job done. Really nicely made seat IMO.
The seats are relatively narrow (but still wide if you know what I mean) but she still has to rotate the seat belt to clip it in, but at least she can now do this herself, and more importantly in an accident she could get herself out of the seat (which she struggled with before).
I notice they are currently even cheaper, at £81.45 on their website.
https://www.halfords.com/kids-zone/c...l-booster-seat