Frequent disconnects on broadband/Asus DSL-N55U router

[#1]

I'm wondering if anyone here can help me find the problem with my connection. 99% of the time it's fine, but occasionally I'll get a random complete loss of internet. This affects wireless and wired connections to the router. I've tried replacing the ADSL filter and cables to the router and, living in a very small flat with only one phone socket, I presume that it's into the master socket.
I have, so far as I can tell, configured my router to the settings provided by Plusnet, deferring to my router only on DNS server settings (letting it get them itself rather than giving it the IP). There are a few sections of my router settings that I think may be contributing to my disconnects but I don't know enough about broadband to say either way. Just some reading on-line has led me to focus on a few settings/router logs that I think are relevant, so I've posted them here.
Some basic settings
Some more basic settings
I thought this might be important...
An ADSL log
The error page I get in my browser when my connection goes down.

I also have a log taken from my last disconnect.

Oct 20 21:19:39 WAN Connection: Ethernet link down.
Oct 20 21:19:39 stop_nat_rules: apply the redirect_rules!
Oct 20 21:20:31 pppd[941]: Serial link appears to be disconnected.
Oct 20 21:20:37 pppd[941]: Connection terminated.
Oct 20 21:20:37 pppd[941]: Modem hangup
Oct 20 21:20:47 pppd[941]: Connected to 00:aa:bb:01:23:45 via interface eth2.1.1
Oct 20 21:20:47 pppd[941]: Connect: ppp0 <--> eth2.1.1
Oct 20 21:21:08 pppd[941]: CHAP authentication succeeded
Oct 20 21:21:08 pppd[941]: peer from calling number 00:AA:BB:01:23:45 authorized
Oct 20 21:21:08 pppd[941]: local  IP address 172.16.61.214
Oct 20 21:21:08 pppd[941]: remote IP address 81.146.176.4
Oct 20 21:21:08 pppd[941]: primary   DNS address 62.6.38.125
Oct 20 21:21:08 pppd[941]: secondary DNS address 62.6.38.125
Oct 20 21:21:09 rc_service: ip-up 5566:notify_rc stop_upnp
Oct 20 21:21:09 miniupnpd[5325]: received signal 15, good-bye
Oct 20 21:21:09 rc_service: ip-up 5566:notify_rc start_upnp
Oct 20 21:21:09 miniupnpd[5594]: HTTP listening on port 34931
Oct 20 21:21:09 miniupnpd[5594]: Listening for NAT-PMP traffic on port 5351
Oct 20 21:22:00 WAN Connection: WAN was restored.
Oct 20 21:22:00 start_nat_rules: apply the nat_rules(/tmp/nat_rules_ppp0_eth2.1.1)!

The disconnects seem to happen randomly. No one else but me has access to the router, and the amount of traffic has no bearing on disconnections. It'll do it when it's in use heavily and (according to the logs) when no one is using it in the middle of the night. Can anyone see anything obviously wrong here?

[#2]

According to our connection logs it looks like a slight pattern could be emerging with disconnections around similar times in the evenings. When that happens it can often be due to interference from electrical goods that use a timer (i.e central heating). Would that tie in with anything set on a timer you might have at home?
<img src="http://community.plus.net/visualradius/generated/image13823708425997.png"/>

[#3]

It probably wouldn't be central heating. It's gas central heating that isn't on a timer. I don't think I have anything else that would act that way either.

[#4]

Quote from: jameskyle

I also have a log taken from my last disconnect. Oct 20 21:21:08 pppd[941]: local  IP address 172.16.61.214 Oct 20 21:21:08 pppd[941]: remote IP address 81.146.176.4 Oct 20 21:21:08 pppd[941]: primary  DNS address 62.6.38.125 Oct 20 21:21:08 pppd[941]: secondary DNS address 62.6.38.125

The 172.16.61.214 is a local IP address of the type you'd get when you end up being redirected to a BT Wholesale holding page when the connection is down. The other IP addresses all belong to BT. That log entry suggests the connection between your ASUS router and the exchange is fine, but isn't being sent on to Plusnet.

[#5]

On the one hand it's nice to think that I haven't done anything silly to cause occasional disconnects but it would be handy if it were just a dodgy cable I could easily replace. I presume I'd now have to pester BT to look into it?
dick:quote

[#6]

If there is a setting in the ASUS to disable its own "You failed to access to the web page that you want" error page, then you might see a BT Wholesale page instead, and then it would be easier to see if all the disconnections are of the type where you end up with a 172.16.*.* IP address. Looking at the graph of disconnects, the ones at 01:30am 19/10 and the 2 on Sunday evening appear to have lasted a bit longer, so could have been caused by something different from the others.
In any case, you'd need to contact Plusnet.