I'll answer my own question. After some muddling around I found the following command gave me the output I wanted including mono output.
ffmpeg -i c:\test\00003.mts -r 30 -s 1280x720 -c:v libx264 -crf 23 -ac 1 c:\test\filename3.mp4
cheers Peter
ffmpeg -i c:\test\00003.mts -r 30 -s 1280x720 -c:v libx264 -crf 23 -ac 1 c:\test\filename3.mp4
cheers Peter