Has anybody managed to interface to a BT VP1000 alarm?

It's a re-branded Visonic PowerMax+, I've obtained a PowerMax+ RS232 interface kit and the Visonic programming software but can't seem to get it to talk to the panel as it seems to keep asking for a "download code" (have tried all the obvious things like the system password, etc).

I'm hoping to either interface directly to it via RS232 or enable the X10 port and interface to it via that, but getting it talking to the Visonic software is the first hurdle!