I've just come to the end of last year's Vodafone £20 for 20gb (with £60 quidco cashback and netflix) - was about to cancel but then saw this - £207 total for 10gb 4g data including £75 cashback - works out at £11 a month.
I never really used more than 10gb, so this suits me!
The deal is for new customers, but the cancellation team matched it (actually I only got them to £11.50, but saved the hassle of cancelling & rejoining).
I know people don't like Vodafone but it's by far the best coverage in my area.
Looks good to me...