I have 3 children, who are and have all been, rear facing until 4 years old. I currently have a 16 month old rear facing and a 3 year old rear facing. My 9 year old is in a booster.
I agree with RearFacingToddlers. There is nothing safe with forward facing a small child. It has to do with physics and children's anatomy, not personal choice.
There is tons of factual information available to you on www.rearfacing.co.uk
The British Medical Journal recommends rear facing.
I quote hem here:
"Many babies are switched from a rear facing car seat to a forward facing seat at 9 kg (8 months of age for a boy on the 50th centile)
Excessive stretching or even transection of the spinal cord can result if a child is involved in a head-on crash while in a forward facing car seat
Rear facing seats are safer than forward facing seats for children under 4 years old
Parents and guardians should be advised to keep young children in rear facing seats for as long as possible"
You can read the whole thing here: www.bmj.com/content/338/bmj.b1994
It is not true that ERF (extended rear facing) car seats are few in England. Quite the opposite. England actually has access to ALL ERF seats on the market. They are ALL sold at the In Car Safety Center:
incarsafetycentre.co.uk/category/extended-rear-facing/
Several high street retailers also sell extended rear facing car seats, and there are several private retailers of extended rear facing.
They are not more pricey then forward facing car seats, that is unless you feel comfortable strapping your child to a washboard from ASDA with a small piece of cloth attached to it and calling it a car seat... (yes I'm talking about car seats for £25 and up)
The cheapest ERF car seat you can buy is the Joie Tilt (RRP £1oo) ,the Joie Stages (RRP £150), the Joie Steadi (RRP £130) all rear facing to 18 kg, that is the average 4 year old child. These are all belt fitted.
For ISOFIX we access to the Hauck Varioguard (RRP £180) and Joie Anchor (not released yet).
These are the affordable priced ones, but they are all better then any forward facing car seat you can buy.
The cheapest rear facing car seat that lasts up to 25kg (average 6 year old) is the Britax Max Way RRP £215.
And believe it or not, in car seats, you DO get what you pay for.
Like stated before they have all been tested to the same MAIN test in order to be sold, but some have gone through a lot heavier testing and passed, making them far better.
Also please read the FAQ section as it takes care of all questions you might have regarding myths of "my child can't see out the window" to the other common one "what about their legs?". 
Happy car seat hunting and I hope you take at least some of this information into account when looking for your next stage car seat. 