Currently on 600mins unlimited texts and 12gb data advanced plan and I noticed I could add 18GB Data for £5 on a rolling month by month in the mythree app
So that would be 600mins unlimited text and 30gb data for £17 per month.
The 18GB Data add-on lets you connects your devices to the internet in the UK using your phone. It costs £5.00 per month and will remain on your account until you ask to remove it. In the first month you will be charged the full monthly amount and receive the whole Personal Hotspot allowance, regardless of when you purchase the add-on.
Data is not rolled over.