I have got the DM 200 and I got it into modem only mode but I am struggling to get a connection, Does anyone have any help? Maybe someone else has this modem working with there own router, mine is Linksys EA8300 Router, How did you do it?
It SHOULD just be a matter of configuring the WAN connection on the router for PPPoE with your PlusNet username and password.
edit: Assuming you've got the above correct, having had a look round, it would seem that a possible problem is that the VLAN ID is not set correctly on the DM200. It seems that it has to be set ( to 101 ) with the DM200 in router mode and then switched to modem mode.
There's also a VLAN Passthrough setting , try changing that if the VLAN ID doesn't fix it.