Game of Thrones - Sky on Demand

I've been hearing a lot of great things about this show so was happy to hear in a recent ad from Sky that it has the box-set on their on-demand service. But whenever I've gone onto on-demand recentley I can't find it. I've tried searching for it but the only things that come up are preview programmes for the upcoming 4th series. I also reset my Sky on Demand box but still nothing. So I was wondering if anyone is getting it on-demand at the moment? Or d'you know why it's not available and when it will be?