A new deal live at Three - all handset / Sim-only 12 month contracts (essential and advanced) with 2GB data or more. Also says it's on mobile broadband contracts but I haven't looked at those. Takes the form of a bill credit in the fourth month. Looks like it runs until December 20th.
Some examples of Sim-only
Advanced 600 mins, 4GB - £15/month down to £11.25/month (possible £30 Quidco)
Advanced 600 mins, 8GB - £18/month down to £13.5/month (possible £50 Quidco)
Essential 200 mins, 2GB - £10/month down to £7.5/month (possible £30 Quidco)