The admin on the group are just trying to help. They offer advice to people regardless of which way they want to face their child - they might mention ERF seats to check the person knows about them, but they don't force people to choose them, they'll offer advice on the safest forward facing seats too. The group has grown massively recently, and obviously when you get a large group of people together you get differing opinions.
As pumpkin said, you can get a Joie Stages from most of the major stores that sell car seats these days, for about £130 (often less if you've got money off vouchers etc.). That does from birth to seven years I think, so comes to less than £20 per year of use. That's also the same cost (or actually I think a bit less) than a Maxi Cosi Pebble which seems to be a very popular group 0 seat, but which will probably only be used for 18 months.
We got a seat that cost £295, but goes to 25kg rear facing, so will be able to use it until he's about six (so for five years as he went in it when he was one). It was a big outlay to begin with but we saved money elsewhere and his grandparents contributed money towards it instead of buying loads of Christmas presents for his first Christmas.
You could say 'if they are so bad why do they still sell them?' about an awful lot of products that are sold... cigarettes being one major example. The law hasn't caught up with the science (although in both cases it is slowly).
