G'day Robert,
I have a cheat for doing this!
Free software called HNSKY, a fast simple planetarium program for Windows.
Download it from
http://www.hnsky.org/software.htm
Setup your location, set the time to midnight, get the display to show the meridian, and then use the F8 and F7 keys to advance/retreat by a day.
Shows me that M31 culminates at midnight on October 22nd here in Kyneton.
And in Pomonal, October 24th
Or, you could spend a bit of cash and get Sky Tools V3.0 which gives you optimum viewing dates and times for all objects.
Check it out at
http://www.skyhound.com/ One of my better investments!
Cheers
Chris