OK, having re-read my previous posts, I have edited this again to make my point more clearly.
Because of the number of older television receivers out there, the stations must transmit content in SD, and that is the same the world over. The content delivery, analogue or digital, can be changed. All that is necessary to enable digital delivery is for the receiver to be fitted with a digital set top box.
However each channel is also given a HD channel to broadcast HD programs, for those with HD capable receivers. However the digital channels are the same, and all of them are capable of delivering SD or HD and HD in its various resolution versions.
The problem that faces the stations is the lack of HD content, there is simply not enough of it to fill the HD channels, and that is a problem world-wide. Almost all new programming is being produced in HD, and virtually all outside broadcast material can be originated in HD.
Braddos comment: 'but from a technical perspective the TV in the UK is far
superior.' is incorrect as the UK uses the same DVB-T standard that is used in Australia.