We went Sainsburys Mobile Sim (seemed to be cheapest) and a £9 Alcatel phone from Amazon. It does calls and texting, no email or internet.
Many kids had blackberrys, smartphones or iphones from year 4/5 in primary. So there is some peer pressure.
I'm going to get on my high horse here about smartphones and iPhones though ... sorry, I know we all make different decisions, but I'm going to say it anyway.
At our primary a 10 year old got beaten up for their smart phone on the way to school in the morning (city centre primary school). You'd think parents and children would change. They have't, because that, apparently, would never happen to their child.
We've also seen kids with separated parents go through £500 iPhones (lost one, broke one, dropped on in loo) like chocholates. The parents both want to "buy" their way into the good books and the child thinks these phones are disposable.
Finally, and sadly, I know enough A&E doctors to tell me that those adverts about teenagers getting knocked down because their using their phones whilst crossing road is not just a scare campaign .....