OK so to close off the Three saga previously posted. It proved to be quite a useful search around the service providers to see who actually offered the best value for my needs. Without a doubt the most important thing to me is data. I'm month on month using over 5GB but I do a lot of traveling so it's hardly surprising. I hardly make any old school voice calls and if I do they are normally for work (and I have a phone dedicated to work not play)
Most providers now offer all you can eat or fat data usage but all bar Three also charge royally for it. You do get lots of minutes etc with this greater cost but that's a waste on me.
So I spoke to a customer service rep at Three and discussed my issue with their contract and thoughts about moving. They walked through some options for me and I've tailored a new subscription to exactly what I wanted at less cost so all round, it's a win.
Sticking with Three then and bought another One Plus Two.