Vodafone have what's called a "data extravaganza" on at the moment. 4x the data on most plans for the same price. Best deal I've seen so far is the Samsung GALAXY S7 Edge with 24gb data for £47 a month, £20 upfront & a free Gear VR headset, plus Gear 2 Fit free from Samsung.
Can also get a "red value bundle" same phone etc for £53 a month £20 upfront, same freebies but includes Spotify Premium, Now TV Entertainment pack OR Skype Sports Mobile included & more roaming data. Seems pretty good to me