I really don't think the UK is as clued in to car safety as the Americans.
In the US:-
They have trained Child Passenger Safety Technicians who offer checks on car seat installs and advice to parents. They are trained by SafeKids and places like WalMart/Babies'r'us have mandatory CPST training for the staff that work in car seat depts.
Manufacturers LISTEN to consumers and when they want high rear facing (ERF) limits for convertibles (seats like Britax 1st Class) they get in to a limit raising 'war' with other companies to get the highest limits. They raise limits on seats to accommodate high weight harnessing (HWH) in response to parents requests.
You can get mainstream (i.e. not specialist/special needs) car seats that rear face to 45LBS (20kg) and harness to 80lbs (36kg).
Federal law says no rear facing before 1 years old AND 20lbs (9kg).
American Association of Paediatricians recommend rear facing 2 y/o AND 30lbs (13kg) or limits of seat (between 30-45lbs depending on make/model).
In the UK:-
No official standard of training or recognised qualification in car seat safety.
Manufacturers don't want to give consumers choice over rearfacing/forward facing car seats and force them to buy imported rfing seats.
No seat except special needs seats or TWE that harness past 18kg.
UK law doesn't specify what age as a minimum for forward facing just a weight (9kg).
I think the UK could learn some lessons from Scandinavia (extended rear facing to 4-6 y/o) and some from the US (higher harnessing weights 65-80lbs [30-36kg])
and breathe.........