No mention of the picture quality.
Could it be the software allows the box to output to the TV as 1080p ?
There was a noticeable difference between the Sky 1080i output and my BT TV 1080p output could it just be that Sky have now enabled 1080p output on the box ?
As already mentioned, there is no change in the broadcast quality. Since the broadcast quality is at 1080i for all the UK HD channels, there isn't anything more that Sky can do with the received signals.
How the signal is processed has been changed.
For the technical amongst you I have noticed the interlace lines a little more with some items such as banners when they are removed. This is a normal behaviour with 1080i videos.
Why do I know this? Well since I've been editing a few videos together and stick to using 1080 at either 25p or 50p as I'm not keen on the lines in my own videos and the source is either 30p or 60p, with the exception of one camera which records at 50i. As I tend to have a few titles & prompts on the videos, the lines would be noticeable. Commercial broadcasts would use that many prompts normally.