Just for those who are worried about any changes happening, you can upgrade your contract one month early at no extra cost. In my case, my Ultimate Internet SIM 600 plan was due to finish in early May, now finishing in early April and moving to the One Plan at £20 per month. Must say that while I sorta wish I moved to the One Plan when it was at £15 a month, including paying off my current contract it would have taken 1.5-2 years to make up the difference to how I've done it now, and £20 is a great deal anyhow
EDIT: Quick question. Can they enforce changes once the 12 months is up and the contract becomes a 1 month rolling contract (eg. limiting tethering down to 2GB), or are they stuck providing me with unlimited tethering until I decide to change to a new plan? And I'm right in saying that, as Three don't have any fair usage policies nor any clauses about changing limits etc, they cannot change these mid-term? In other words...what I've signed up for now, will it be indefinite? Have a good idea but would rather someone who is more clued up than myself confirm this! Thanks all