Dear Tony...thank you for your interest.....
I could not get PD to burn on my laptop (although powerful) and so copied the files and PDS file to my desktop....which burned fine. (same spec as laptop)
I had however also used another program to burn a copy of the finished video and that was ok (on the desktop again)
I wonder if it may be that they laptop is struggling with such a large task and is overheating (despite running a large fan alongside it!!!)
However, I am going to see what happens when I try to burn something more sensible in size as this was approaching the Blu ray max size......a lot for any pc and /or program top handle.
Best wishes
Ray