Hey Schwarzeradler,
I went for Vodafone, I thought they have the most competitive online deals for new customers. They were the only ones who offered 12 month contracts, which was my only option, and it comes with the iphone by paying a slight premium depending on what tariff you go for. I was with o2 for 7 years and I do not recommend it, they are not as competitive and their customer service has been really bad for me at least. Bear in mind I went for a plan with lots of minutes so I did not have to pay much for the handset.
hope this helps.
I went for Vodafone, I thought they have the most competitive online deals for new customers. They were the only ones who offered 12 month contracts, which was my only option, and it comes with the iphone by paying a slight premium depending on what tariff you go for. I was with o2 for 7 years and I do not recommend it, they are not as competitive and their customer service has been really bad for me at least. Bear in mind I went for a plan with lots of minutes so I did not have to pay much for the handset.
hope this helps.