Well, this actually is a different router. I had a Billion 7800DXL, but there were two things with that. Firstly, the WiFi coverage wasn't great, and secondly, I had problems a while back with complete loss of connection on several occasions. IDNet couldn't find a solution, although they did acknowledge at the time, that the problem looked to be with the exchange, or some other outside factor. In the end, they suggested going on to PPPoE, rather than PPPoA, and that seemed to resolve the issue.
This was some time back, and recently, I came across an Asus N55U for a silly price on eBay, so thought I'd give it a try. It virtually set itself up, and you could choose your ISP from a drop down list, in which IDNet was included, so I can only assume that all the settings are correct, but the settings look quite familiar. It is, however, now back on PPPoA, but this issue isn't the same as before, in that I'm not totally losing DSL, at least, not for more than a minute or two. So, I don't really know if this is the same issue as before, only presenting differently due to the different router, or it's something else.