Hi Graham,
Thanks for the advice, but I think that it is a little too involved to be a regular task.
I can't understand why a format that is so popular has such a major shortcoming.
My son is going to bring his PS4 round, to see if the extra processing power can manage to play them better.
The file I converted to 50hz with All Video Converter plays perfectly, so I think that might have to be my solution for now.
Once I get the input and output paths set up it should be relatively easy to get the conversions going, then leave the PC to it, while I get on with something else.
Regards,
Paul