@Steve_M1 you are not first to mention making channels easier to reach by one means or another and I doubt you will be the last. I tend not to use the HD channels myself with on the smart box or my TiVo as they don't have all my regional content which is rather annoying. The star button is already used for switching subtitles on and off so I doubt they will change that.
@Steve_M1 If you go to this section on the boards http://community.nowtv.com/t5/Ideas-for-NOW-TV/idb-p/My_Ideas you can suggest ideas if they get enough interest they may include it in the future it has happened with a few.
The Now TV Smart Box uses standard Freeview channel numbering and Freeview insists on placing HD channels from channel 101 - blame them for their stupidity in not changing this since HD launched - it isn't this boxes fault.
you're quite right @Justdoit - it's not the boxes fault. However it's not hard either for NowTV to make the channels more 'navigation friendly' either by adding 'favourite channels' functionality or by making a 'HD' category.