On a serious note, i'd probably join if there actually were a proper mathsoc with a decent amount of members (assuming we're not automatically part of it by doing maths).
If you really are keen on reviving Mathsoc, you should go and see Jim Franklin about it. I think he has the Mathsoc bank a/c stuff.
Mathsoc doesn't really work as a society as there too few members (especially ones willing to be active) and since most of us are doing combined degrees, our interests are quite different.