Thanks for your suggestions guys. I got it working, had to uncheck the
box block private network connections.
The setup is this:
internet -- cable modem in stb -- linksys router -- home network of 3 pcs
internet -- cable modem in stb -- linksys router -- m0n0wall -- my pc
now the m0n0wall internal network has ips 192.168.0.x and the rest of my
home network (including m0n0 WAN and the linksys) 192.168.1.*
It all works fine, regards to the net connection to my pc, but obviously
the networks are seperate. Any ideas of a way to bridge the two, however
it isnt really important as at uni I will definitely want to be seperate.