[onion2k]

That's true on every network except Three. Unlimited data on Three genuinely does mean unlimited without any restrictions (well, one actually, data used tethering your phone as a wifi hotspot isn't included). You could download a terabyte of stuff for £20/month (about $25).

[sleepychu]

I'm 15GBP/month with Three for unlimited data, 4GB tethering which is fine for the occasional train journey of email/twitter.

[danielsamuels]

I have 12GB of tethering included in my £18/mo unlimited plan.