Connected to gateway but not dns server
Maybe it was sons ipad. He pulled up in the drive earlier!! 
I had turned off the wireless when I did the ping test. Son just dropped by this morning for 10 minutes, you know, long enough for a drink and toast! As they do. 
OK. I don't think we are going to glean anything further that's going to be useful, so a modem/router and filter swap would be a good idea.
Now one thing I didn't mention in my previous post about swapping things, is because you are on a very long line, it will be subject to quite a bit of interference after dark due to AM/MW propagation. This will reduce the SNRM and any resync will then be at a slower speed. So change it and the filter if you have a spare, in daylight, a good hour after sunrise and a good hour before sunset.
Then post the new modem/router stats and some ping results
Edit: Is that Belkin a v1, v2 or v3?
I will try and do it tomorrow pm. Too busy in the morning unless by some miracle I am up at six. Have a funeral to attend on Friday, so won't post anything until Saturday probably. Don't need a filter. Not sure which version it is, that info is not on the box but I have had it about four years so maybe a v1. Re after dark interference - perhaps there are vampires about.....
Now be careful, all this tweaking noise margins means that you are resyncing. DLM will be looking at these as dropped connections - at least I assume that's what you are doing from the way you phrased your post. If you are simply rebooting and posting back the new values, then as far as DLM is concerned, that is just as bad. If it raises the Target SNRM because it thinks the line is unstable, you will end up with slower speeds.
Now, although I take Chris's point on board, I was going by a previously achieved sync speed from the Delta reports that Chris provided which suggested that your line might/did achieve a sync (Data rate on yourTP-Link Belkin) of 1728 which gives a profile of 1.5Mbps and if that was achieved with a 6dB Target SNRM, it suggests that your line attenuation might be close to 64dB rather than some unknown figure that is possible somewhat higher than 63.5dB. If your line length is about 6km then this suggests that either you are on an excellent copper line (possibly 0.9 rather than 0.5 copper - it has been used in some rural locations) or that speed was achieved with a tweaked SNRM which is fine IF your connection can hold it and is stable.
However, it would help significantly to know if that was the case, then we can stop being concerned about something still being wrong.
As far as the recent speed tests go, that last one being a bit slower, might just be normal variability, such results can vary from test to test and a one off value cannot be relied upon. TBH, you want to forget speed throughput results for now, as it's the sync speed and profile that are the important things. Throughput speed will follow the profile (usually just below it).
Now, if you are not tweaking the SNRM, it could be that theTP-Link Belkin is misreporting the SNRM - I have come across this one before as well.
Bearing in mind you are on a 20CN connection, this unfortunately means that if you have a lower sync speed which drops your profile to the next band down, it does so immediately and even if you then achieve a slightly faster sync speed that would put you into the next profile band up,. it's only a small change and can take 5 days for DLM to up the profile (and then your Plusnet Current Line speed (Login required) has to catch up which may also not happen immediately. So stability at a sensible speed is imperative. A sync speed of 1440 or just above would give you a 1.25Mbps profile after a of stable connection with no drops.
So really we need to know the following 1) Are you tweaking the SNRM? 2) Is the SNRM changing somewhat during daylight hours? - it will drop some between dusk and dawn. 3) Is the sync speed (data rate) remaining stable or is the connection dropping?
Edit: correct modem/router brand to that which OP referred
Now, although I take Chris's point on board, I was going by a previously achieved sync speed from the Delta reports that Chris provided which suggested that your line might/did achieve a sync (Data rate on your
However, it would help significantly to know if that was the case, then we can stop being concerned about something still being wrong.
As far as the recent speed tests go, that last one being a bit slower, might just be normal variability, such results can vary from test to test and a one off value cannot be relied upon. TBH, you want to forget speed throughput results for now, as it's the sync speed and profile that are the important things. Throughput speed will follow the profile (usually just below it).
Now, if you are not tweaking the SNRM, it could be that the
Bearing in mind you are on a 20CN connection, this unfortunately means that if you have a lower sync speed which drops your profile to the next band down, it does so immediately and even if you then achieve a slightly faster sync speed that would put you into the next profile band up,. it's only a small change and can take 5 days for DLM to up the profile (and then your Plusnet Current Line speed (Login required) has to catch up which may also not happen immediately. So stability at a sensible speed is imperative. A sync speed of 1440 or just above would give you a 1.25Mbps profile after a of stable connection with no drops.
So really we need to know the following 1) Are you tweaking the SNRM? 2) Is the SNRM changing somewhat during daylight hours? - it will drop some between dusk and dawn. 3) Is the sync speed (data rate) remaining stable or is the connection dropping?
Edit: correct modem/router brand to that which OP referred
Data Rate has remained at 1376/448
noise margin started at 4.5 around 09.30am - it has changed up and down all day, starting at 3.4 at midday 3.3 at 1.00pm 3.5 at 1.30, 3.1 at 2.00, down to 2.8 at 15.09pm.
found an old set of stats from the same Belkin modem (2011) 1728/448 5.2/13 16.7/12.3 63.3/31.5
noise margin started at 4.5 around 09.30am - it has changed up and down all day, starting at 3.4 at midday 3.3 at 1.00pm 3.5 at 1.30, 3.1 at 2.00, down to 2.8 at 15.09pm.
found an old set of stats from the same Belkin modem (2011) 1728/448 5.2/13 16.7/12.3 63.3/31.5