After a lot of effect I've got to the point of having a remote
VPN client connecting to a BM3.8 server which is not on
the networks default route. So what is the process of
allowing the client's packets to be routed around the office
network correctly?

So far I have

a) used filtcfg to allow access to the VPN lan on the public
interface of the BM server as that is where the address
translation takes place.

b) on a internal test server configured a route via tcpcon to
allow the routing of packets to the VPN lan via the internal
interface of the BM server.

Both of these have worked, but how can you get the BM server
to publish a RIP route to the network as you can not set up
an active route to a local interface?