I'm sure you know this, but virgin mobile is just EE 3G.

I would not touch O2 with a baregpole given my experiences of their data. I have a SIM with them but it's PAYG and I rarely ever use it.

I also have a vodafone SIM, anywhere that is not a city centre is 2G.

In terms of data, 3 probably have the best deals but I find calls really poor...,
If you want decent data, signal and call quality EE cannot be beaten in my view.

Get pretty good 4G out of towns and city centers with Vodafone recently.

I get pretty good 4G with EE, but then again it does flicker out and in of 3-4g, but then again i think thats my phone playing up. it is pretty old ( iphone 4 O_O )

Not sure how it would flicker into 4G. The iPhone 4 didn't support it.

It doesnt support 4g

maybe between 3G and HSPDA.

i just realised (stupid me) i miss clicked on 4 instead of 5, sorry everyone, you all properly think im mad :').