As far as I can read, Sky do not offer a static IP, monthly fee or not.
Sky also, do not allow any router to be used other than their own, they do have a DynDNS service, but DynDNS is no longer free, nor can you have an account for longer than 14 days without paying. Those who did register before the change in 2013, can use the free account if they log in monthly.
What about this No-IP, I'm assuming it can't get my dynamic IP from the Router, but rather a computer let's say - which has to be on 24/7?
Frazer.