Thanks Chis, It's been at least a year, but unfortunately I'm talking about the BT Community forums not Plusnet.

I've tried raising the issue, I've tried signing up with different usernames, all have been banned, it's as if the moderator NeilO is carrying out a personal vendetta against me which is a bit odd given I'm a paying customer and he's in Customer Service, but meh.

I'm happy enough ringing on the personal helpline I have in the UK rather than dealing with the brick wall of India anyway.

Also got banned from BT Community forum for posting the full story of what happened with the customer service team. Apparently criticising BT only lands you in trouble.

OK well another Openreach visit today and they did manage to recover most of my speed back to a connection rate of 47.5Mbps back up from under 35Mbps.

Not all good though as some of this will be down to interleaving coming off with the DLM reset, it's still below the 51Mbps I had before the first Openreach visit on 12/04/16 and not 1/2 hour after the guy left my SNR instantly dropped (N.B. Not a decline but a sudden drop) from 6.2dB to 5.5dB along with a sudden drop of some 1Mbps on the max achievable line rate. The max attainable line rate is currently sat at some 1.6Mbps less than the actual line rate.

As expected errors are through the roof again so no doubt once DLM introduces interleaving again I'll drop further.

So to sum up some improvement, I believe they are sending another Engineer out to check for REIN along the route to my cabinet but will have to wait and see I guess.

The sad thing is why Plusnet and Openreach put me through this in the first place, it's fairly obvious now I was right not just to put up with it or leave as there is actually a problem that needs fixing.

Have you tried another modem or power brick? Could be noisy..

I've tried:

HH5A (Useless waste of plastic that they are)
ZyXel SBG3300-N great bit of kit
Netgear D7000 another great bit of kit bought to replace my SBG3300-N as it has 5Ghz wifi and the SBG doesn't
ECI Modem
Huawei Modem (Unlocked)

Best results are with the ZyXel and Netgear.

As I said I know it's not my equipment, this happened on every Openreach visit and was noted at the time.

Sorry,poor attention span
So which modem are you using currently?

Currently on the Netgear D7000

Ah thanks, misread the posts!

Hmmmm not all good today.

I'm now seeing sudden drops and increases in SNR of exactly 0.7dB every few hours. It drops 0.7dB stays that way for an hour of two then jumps back up 0.7dB and stays at the higher level for an hour of two, repeated all day until around 5pm when the SNR stays at the lower level then slowly drops as the evening comes in.

No idea what is causing these sudden changes in SNR/max attainable speed since yesterday though.

Anyone have any ideas?

The evening slow drop is normal - to do with the sun having set. It will rise with the sun in the morning.

A frequent 0.7dB drop/rise points to a single electrical or electronic device being switched on and off, either by a time-switch or a thermostat. The fact it stays down from 5pm'ish suggests central heating or even just the hot water tank, but it may well be nothing to do with the heating.