Bagpuss & Mumbojumbo
It must've been really frightening when you had the accident and I'm so glad the kids were okay - doesn't matter how the seats end up as long as the children came out unharmed.
Mumbojumbo - I haven't a clue what I'm going to do. I worry that at only 33 months, DS1 is too young for a booster without a 5 point harness and that's my real issue. However, he is 100cm tall and 15.75kg so a big boy for his age.
Re the tests - this is what Which say about them:
To meet the compulsory standard (called ECE R44.03), all child seats sold in the UK must be able to withstand a low-speed front crash test, equivalent to around 30mph, without a child sustaining any serious injury. The frontal impact is done on a test bench, rather than with the seat fixed in a real car. These crash tests for child seats don't yet include a side-impact test.
Our own tests
When we test child seats we use far more stringent (and realistic) standards than the legal requirements. We use the same severe EuroNCAP-derived crash situations used to assess adult protection. This means, for example, a front crash at about 40mph and also a side-impact test. We put child crash test dummies in car seats fitted to real car bodies. The front crash is equivalent to a force of 30 times the dummy's weight on impact, rather than just 20 times in the standard safety test.
The seat anchorage points in the test car body and the car seat characteristics are also more realistic than on the standard's bench test.
These tests reveal big differences between seats. Though all meet the official standard, some cope much better than others in our more stringent crash conditions.
So that points me towards the Kid but it's the old harness thing - seems like our children are around the same ages so you're probably thinking along the same lines as me.
I think I'll do what Bagpuss suggests and phone the Britax helpline, that's a good idea. Better do it today as I'll need to get the seat back soon if I'm exchanging it - DS1 had a bad fall yesterday and knocked himself out ... only for a minute or so but we still had to go to A&E and have him checked out and x-rayed so the car seat issue got put on the sideburner!
I'll keep you posted but let me know what you decide to do.