It's well documented that the M240 is not able to go past 8 seconds shutter duration when set at ISO 800 and further which makes successful Milky Way type of pictures very difficult (standard being something like 30 seconds at ISO 1600 at f2). Well after some searching today I found a post where a guy had discovered that using the M set on auto ISO and in continuous shoot mode when set on bulb he could get 60 seconds. However even when auto ISO high limit was set at 3600 ISO the exposure turned out at 800 ISO the camera not shifting the the highest ISO in the auto setting. Anyway after some experimentation I found that if I took a shot first in A shutter mode at ISO 1600 and then go back to auto ISO it would still use 1600 since auto ISO uses the last used ISO when set to bulb. So with this I was able to get and exposure of 60 seconds at 1600 ISO when ISO is in auto, shutter set to B and in continuous shot C.
Recap
Set auto ISO upper limit to 1600 or above
Set ISO to 1600 and take a picture
Set ISO to auto
Set shutter to B
Set shoot mode to C
Take a shot and hold down the shutter button
After 60 secs it will automatically close the shutter
Of course in the real world you would use a cable release and make the necessary exposure time, say 30 seconds for the Milky Way at f2
Now I just have to find somewhere to shoot the Milky Way which is not easy when you live in Shanghai :-)