USB - RS485 DMX interface problem

[BurningTantalum]

I posted a thread in Repair section a few weeks ago concerning three 36 LED RGB stage spotlights that I had acquired for repair.
I have three working LED spot lights now, and decided to have a play with the DMX interface just out of interest. I found the cheapest USB to RS485 interface on eBay and ordered it (I didn't want to spend too much time getting involved in knocking up an interface...)

This was the item: http://www.ebay.com.au/itm/USB-to-RS485-Converter-Module-for-Computer-USB-RS485-Port-PL2303-Drive-S-/191736124887?

I struggled to sort out a driver for the interface but finally got a PL2303 driver that 'worked'.
The chip on the interface is a Prolific PL2303 (or clone) with a MAX485.
I downloaded copies of QLC+ and a couple of other lighting control programs suggested on the previous thread and installed them on an old workshop XP laptop.
I cannot get any of the programs to recognise the interface, and the only theory that I have is that they will only work with FTDI chips.
The PL2303 is recognised by name by '232Analyzer' so I assume that the interface is working.
Has anyone any experience of this issue.
Is my theory correct, so do I need to knock up/purchase an interface with an FTDI chip ?

Regards, BT