ASUS DSL-N66U Modem/Router

[#1]

There is this thread all about the ASUS N66U.  There is stuff in there IIRC about problems and settings etc for ADSL as well as FTTC without re-reading it. It may be of some help.
It looks as though you are on ADSL there pepperrell, so you will need to end up with the settings as reply #4, otherwise it will be as redbull2k14 mentions.
However, I suspect you may be suffering from what appears to be this stale session issue.

[#2]

Thanks, everyone.
1. I'll raise the stale session issue with the CSC - I have an open fault at the moment.
2. I'll also try the firmware update - I have a Heath Robinson arrangement of a smartphone, an android tablet, a laptop and a USB pen drive, so I should be able to manage. 
3. Depending on the outcome of those, I'll try to reset as PPPoE reset.
4. Re the IIRC I'm not v tech-savvy (as you will have concluded by now) so the specialist technical dialogue is way over my head.
Many thanks to all for your help - much appreciated!

[#3]

If you are on ADSL your final settings should be the PPPoA ones.