The reason for 1080p is for blue-ray, hd dvd, or pc connectivity. Even in those cases it probably will not make a significant difference. As far as Sky, they may eventually have a 1080p selectable capable STB in the future but the transmissions are likely not to be 1080p so it won't make any difference.
if you're watching video - like a footy match, then it isn't being recorded in 1080p for the foreseeable future.
If you're watching a movie in 1080i, then it has all the informaiton there, as movies are only 24fps, not the 50 of 1080i. So a good deinterlacer on a TV or projector would be able to recreate the full 1080p image of the original.
1080p is just something the marketing guys are throwing out there to make their stuff seem better than yours.