Errol,
I agree that the version 3.0 tool has many functional improvements, unfortunately it has also created several major software bugs including issues which did not exist in the previous version.
You certainly could add items to the GlobalKeySpecification.xml and whilst it should work I would not recommend it because it may well show up unknown issues because it would not have been tested with the current tool version. In my view, the best and safest way is to add your requirements to the product XML file because most things you would wish to do on a regular basis would be associated with a product, whether B&O or 3rd party.
I have not looked at the "DVB-T/S UK" issue you raised but I expect that this is associated with the fact that on later Beovisions the TV button can be assigned to TV and the software team have assumed this is a fact for all TV's when it is far from true.
With regards to your Hitachi.xml source line for volume up which I can confirm has a standard NEC protocol address code of HEX 50AF and the vol+ command code of 12ED.
If you are going to use the firmware generated NEC code as you have done, then you need to know about a flaw (software bug) in the repeat code section which means it does NOT conform to the NEC spec. This means about 40% of products which use the NEC protocol will not work correctly, but I have produced a workaround for the problem which works 100%.
When you press a button it sends a code with the standard start bit of a pulse of 9 milli seconds and a pause (space) of 4.5 milli seconds. If you hold the button it does NOT send the command again, but sends a start bit of 9 milli seconds followed by 2.25 milli second pause then one (1) data bit. The problem is that the Beo5 sends a standard pause of 4.5 milli seconds so the receiver thinks its the start of a new command when it is not. See the diagram below to fully understand the situation.
Having said all that when it comes to volume up and down you don't want a repeat signal at all, you want one seperate signal per click as you turn the remote wheel and that's the next problem to overcome because it still does a repeat signal when you don't want it.
I have created a Hitachi Generic XML file for you to test and look at the code which resolves your problem.
The following hard keys only have been programmed STEPUP, STEPDOWN, VOLUME UP, VOLUME DOWN, PLAY, STOP and you can download it from HERE
Extract the file from the ZIP file and extract to C:\ which will automatically put the file in the correct directory of the Beo5 Configuration Tool