I've spent ten minutes wading through pages of info on the Sky website (and continually going around in circles) and trying to phone them for a solution. I'd just found a way of accessing the 'live chat' option (by going via 'complaints', rather than 'help' in their menu options) when I saw that you'd beaten me to it.
Sky's so-called help system is nearly as bad as BT's for promising much but offering little!
However you'll lose all of your existing recordings and you won't be able to record anything new.
Alternatively you could replace your Sky+ box with something like this, which would enable you to view and record Freesat channels:
Amazon.co.uk User Recommendation