I haven't used O2 for over a year now, since I last used them, 4G has been rolled out in my area so I want to give them another go. I use a cheap sim-only deal with Three as my main sim, I've used EE when they did the Dan and Phil sim, and I'm using their current 100GB sim also.

So I'm looking for the cheapest way to get data on O2 and, why not, Vodafone too. Tesco and Lyca are cheap ways of using the O2 network, but I don't know if I'll get the same experience/speed? I was thinking of getting a data sim and using it in a phone, will that work or will a data sim be restricted to only working in a tablet?

I don't need calls or texts. If anyone has any suggestions as to the cheapest way of using O2 or Vodafone's 4G network on a phone, please share!