The five main channels and S4c will have HD from 2009.
It will be transmitted via freeview by region by region as they go digital. So North west will get it first as the are digital already.
I would think these channels would be available to cable and sky. To complement the beeb HD.
Although this is really freeview news it is to show these channels available soon.
However those with freeview boxes dont go jumping up and down. It wont work on standard freeview boxes even your built in ones in your HD ready tv's as I understand as the multiplexes are to be moved and it will need a DVB-T2 reciever to get HD anyway.
http://www.ofcom.org.uk/images/nr/multiplexes
http://www.dtg.org.uk/news/news.php?id=2962
However VM wont get new HD until they solve there own bandwidth issues.
Hopefully they will get it sorted soon VM dont want to find themselves behind freeview in HD.