Sign up to Top Cash Back
https://www.topcashback.co.uk/home
Scroll through the product options at the top of the site (after signed up).
Go to mobile/sim providers and find E2Save (the one with the £5.50 deal.
The E2Save site explains how to get your cashback much better than I can - you...
Well the best deal I could find is the Vodafone 8GB that you've been quoted for.
£5.50 pm after cashback redemption.
You can get more cashback at the website 'topcashback' if you go via their website...