Looking to change network as my current 5gb for 10 has caught me out a couple of time. Usually holidays where I have no WiFi. Ive found a deal for 10 for 10. Its a 12 month rather than month rolling. Its with sky and seem to do a 3 year data rollover! Which actually sounds too good to be true. Looks like 50 pounds cashback too! Before I commit is this a particularly good deal?