The good news is that CNet quotes the BBC saying "1080p25 uses less capacity than 1080i25 and less capacity than 1080p50 ... There is no 24p in the Freeview HD system. It's not practical to switch between 25p and 24p on programme boundaries as this would cause displays to get upset." and says that the BBC has ruled out 720p completely.
So, all programmes will be 25 frames per second, 1,920x1080-pixel, with interleaved scanning used for live and studio events and progressive used for drama and films.
This is good news, as this will double the resolution on Freeview HD to five times that of analogue and Freeview. This is a much easier sales message than 2.5 times of 720-line and puts it on par with Freesat HD.
On the matter of 720i, that the original Ofcom consulation on DVB-T2 asked Question 17: do you agree with the proposal that HD broadcasting on the DTT platform should use the more efficient progressive format,rather than the interlaced format?, but with the annex listing 720p and 1080i.
Under the "720p 1080p 1080i" scheme, "normal telly" is 576i25, with 25 frames a second, but 50 fields of interlaced picture, effectively at 720x288.
Mark A: SD signals have 576 lines per frame, interlaced.
Public Service channels - the old analogue channels - are required to use 720 pixels per line, the same as usually used on DVDs. Commercial channels are allowed to reduce this to 706 or 544 pixels per line. Many of ITV's secondary channels use the lowest pixel counts even for widescreen pictures, which were really intended for use when broadcasting 4:3 pictures (544 pixels is roughly 3/4 of 720 - a 4:3 picture is 3/4 the width of a 16:9 widescreen).
These pixels are not square. A widescreen TV has a ratio of 16:9 or 1.78:1. 720x576 is a ratio of 1.25:1. The pixels are therefore 1.42 times wider than they are tall, or 0.7 times as tall as they are wide. This is the 'Kell factor'. A 544x576 pixel widescreen picture has a 0.525 Kell factor.
Freeview HD is using 1080 lines per frame. Most broadcasters are using square pixels, 1920 pixels per line, but the BBC are sticking with a 'Kell factor' of 0.7 and using 1440x1080 (interlaced), which substantially reduces the bitrate needed.