Until May 18th, Giffgaff's offering incredible data deals with unlimited calls & texts.
You'll get £10 back with my link (so will I):
http://www.giffgaff.com/orders/affiliate/cherr674_1778286806256
On 18-month contracts, SIM only:
75GB - £10 a month
150GB - £12 a month
300GB - £15 a month
Unlimited - £25 a month
Rolling monthly plans, SIM only:
40GB - £10
75GB - £12
150GB - £15
300GB - £20
Unlimited - £35