Which canes do I use ....

First of all, welcome Matthew.

This is the patent method of one of our well respected members of growing runner beans.

http://www.chat.allotment-garden.org/viewtopic.php?t=2100&highlight=munty+bean+frame

Your should not need support for broad beans, but you could stake around the patch/row & run a string around them if you are in doubt.

If the french beans are dwarf ones, they don't need support, they support each other, if they are climbing french beans - as per runner beans!

I stake my runners like this...