Coreplayer: didn't help. I had read that you could go to Select Page....Video and change type to RawFrameBuffer, but this did not appear as an option, I tried the rest. Once I put these two files in you can go to Preferences, but no longer Select Page. Coreplayer crashes as soon as I try to load an mp4 file.
Fortuna: was crashing on startup. Now seems stable. Won't play my mp4 file but can keep experimenting with file types now. Crashes on exit.
Shinco: was crashing on load file. Now will not load.
I found a program called MioMediaPlayer (presumably belonging to the V735) built into the system and copied this into the programs, set one of the icons to load it. It seems to play video files fine first time and stably. Still seems to crash on exit a bit but seems to be OK if you just set it to play a video and don't mess around with it. Will leave it running over the course of the day and test a bit more.
For anybody interested these are the steps I took.
Copy MioMediaPlayer into Visual programs folder from root/Program Files.
Go into the Scripts and change the Flash player load script path to load the MioMediaPlayer instead of Flash - just cos I won't use the Flash player.
So this might help others having a similar problem.