Vodafone is having a winter sale.
The Red XXL package has dropped from £40 to £30.
12 month contract
20gb with full tethering.
60 quidco plus a choice of either a Netflix, Sky go, or Spotify subscription.
Factoring in the quidco payout and spotify account ( which I pay for now) my effective price is £15.
The tethering and the better reception pushes it past the post in front of three for me.
Your mileage may vary.