Three questions - I'll start with the last first!

So I finally took the plunge and installed CbB - seemed to install ok but I took the option not to include the extra content as I have Home Studio and so have the Studio Instruments already - is any of the rest of the content worth having for me? - I understand Melodyne is just a demo version. If I do need the extra content will I have to reinstall?
 
I can't get my A Pro 800 to register in CbB - fortunately it still works ok in HS so for now on I will continue to use that but hope that there may be a solution. I have the midi settings set up the same as in HS but noted that when I go into controller settings there are none available
 
Also, although Garritan Personal Orchestra opens in CbB none of the instruments will install in the midi channel slots on the interface - very strange - again all seems ok in HS
 
Any help much appreciated!

Regarding Garritan Personal Orchestra, does this help?
https://www.cakewalk.com/...elp=SoftSynths.04.html

For the A800, I would start with reinstalling the drivers for it. I just loaded a new Win10 machine and had to reinstall my A300 drivers a couple times during the process of loading the machine, but forget exactly where it fell down.
 
Garritan also had some loading pains, because I also use sforzando, and they seem to conflict if not loaded in a specific sequence. If you are using just Garritan, check the setting tab in the UI (far right) and check for updates on the two components near the bottom (ARIA player, and I forget the other). A reload of those, even if current, may also help.

Thanks I'll try those ideas!

Ok reinstalled APro driver and still no response to keyboard - I don't think that was the problem as Sonar HS is working fine with the Apro as is Ableton Lite with various VSTs
 
Checked updates to Garritan - current versions are indicated at both buttons. Weirdly now though Garritan is loading the instruments ok but still no sound either from playing the Apro or from the GUI keyboard - again both work fine in HS. Also UVI GUI keyboard appears to work in CbB (but again Apro doesn't).  I opened a midi orchestral piece which used Garritan which played fine. I do have Sforzando installed so that could be an issue as mettelus suggests.
 
Wondering if it is worth persevering or whether to stick to HS? - I'd rather get CbB to work with A-Pro and Garritan to keep updated but I am just a hobbyist so don't necessarily need the extra bells and whistles of CbB
 
Thanks for the help so far 
 

All very strange but.......I moved some of the controllers on the Apro and noticed they were transmitting and suddenly the keyboard began to work as did the GUI keyboard in Garritan! All I can assume is that one of the controllers on the Apro was set in such a way it was reducing the volume to 0 - though why that would not be the case in Sonar HS I have no idea! Hopefully two of my problems are solved now though I know from experience the Apro can be temperamental! 
 
So that brings me to the other question - is the extra content offered at install worth having and is it necessary to reinstall to get it? I'd be reluctant to uninstall CbB to reinstall now I appear to have got it working and as it may affect some of my HS settings / files
 
Thanks again for the help!

It is possible to install add-ons at any time. Click the down arrow to the right of the Open button to get the install add-ons option.

Only you can decide if the add-ons are of value to you. Aside from adding features, installing them should not have any impact to your existing software.
 
The Theme Editor is a stand alone tool to modify CbB UI colors and images.
Here is some info and a few videos about the Drum Replacer
 

Thanks very much - I'll check that out later :-)

Remember, with Garritan Personal Orchestra, sending a CC1 ->  0 will mute the volume of most sounds.  For this reason, you might want to deselect the option "Zero Controllers When Play Stops" in Preferences | Project | MIDI

Thanks will look at doing that. Though UVI workstation loaded with Digital Synstations was also silent and did not appear to be receiving midi from the keyboard until it suddenly was! I'll see how things are working today!