**This deal has now expired BUT: the £20pm for 20GB is BACK!! So I'll look out for that one posted soon ¬.¬
I don't know how much it is per year but since only about 4 people in the UK pay for their year's SIM only contract upfront I don't overly feel the need to do the maths.
Quidco seem to be offering £27.50 at the moment.
If paid out with the Tesco App it would bring the monthly payment down to £7.50ish a month..Bargain