To add to my previous post:
The new BBC HD channels will be available as follows:
BBC3 HD will share capacity with CBBC HD the same as with the SD versions, on the BBC B Mux replacing the current BBC Red Button HD. These channels will be available from all Freeview transmitters.
The remaining BBC HD varients will take capacity on the new COM 7 mux, which will only be available from 29 of the 80 full freeview transmitters. A map of the COM 7 transmitter sites can be found
HERE
All the new HD varients will be available on Freesat & Virgin.