I would avoid 3.
I was with them for 4 years, and 4 different handsets, all of which went faulty within the first year, may be a coincidence, but since leaving for O2 none of my phones have ever had an issue.
Their customer service is appalling and their coverage is shite.
I actually ended up cancelling my last 24 month contract 10 months early, despite having to pay them about £300 to do so. I was that desperate to leave.
They then offered me a free 32gb iPhone, unlimited calls, unlimited texts and unlimited data for something like £15 a month, just to keep my custom. I still turned it down and paid double that at O2 and paid £100 for the handset.