@Nicholas_Waterton #1 - see my post regarding setting up MaryTTS as a separate service and integrating into OpenHAB rules. This gives really good results compared to the MaryTTS binding.
#2 - look into using pulse audio for remote playback. I used this with good results for sending the MaryTTS output from my server to remote Ubuntu Desktop(s). This is much more reliable than bluetooth, and doesn’t involve pulling cables 
An example of this is included in my script (under REMOTE PLAYBACK).
Best regards,
.