Connection constantly dropping and very slow speeds.

[#1]

Since Friday 3rd July we have been experiencing problems with connection dropping out and a web page coming about a Technicolor asking for a login details?  Then without me doing anything all is working again although speeds are very slow;  BT speedtest showed the following;
Download speedachieved during the test was - 3.81 Mbps
For your connection, the acceptable range of speeds is 0.6 Mbps-7.15 Mbps.
Additional Information:
Your DSL Connection Rate :5.09 Mbps(DOWN-STREAM), 0.45 Mbps(UP-STREAM)
IP Profile for your line is - 4 Mbps
This morning is terrible with connection dropping out and staying down for up to 20 minutes.  Hardwired the modem to the PC and still no connection to Internet.  Changed the filter and plugged irt directly into the master socket and still no connection.  Phone line works okay.  When connected the speeds are very slow.  Trying to phone Plusnet is a joke as automated message tells you of waits up to hald and hour!  Ridiculous.  I think I would rather pay the extra and have a decent customer support  team, but where does one go?
BTW as I have paid the line rental up front until about March next year surely I can still change the broadband and phone line to another supplier as ultimately the line is rented from BT who have been paid?

[#2]

Just to add.  I ran a test 5 minutes ago while I was connected and here are the results;
Download speedachieved during the test was - 3.78 Mbps
For your connection, the acceptable range of speeds is 0.6 Mbps-7.15 Mbps.
Additional Information:
Your DSL Connection Rate :8.13 Mbps(DOWN-STREAM), 0.45 Mbps(UP-STREAM)
IP Profile for your line is - 4 Mbps

[#3]

There seems to have been a few drops this morning.

Our tests aren't showing any issues or outages.
If the drops continue I'd recommend raising a fault using the link below.
https://faults.plus.net

[#4]

It's worth noting that your first BT speed test shows the correct IP Profile for the connection speed, assuming ADSL Max.
Your second shows you are back to connecting at 8128kbps which in between 4 hours and a couple of days should give an IP Profile of 7.15Mbps and restore your speed once the Plusnet Current line speed adjusts to match that. I believe that should happen within a few hours of the IP Profile rise.
None of that solves the question of why you are getting the drops of course :(. But it does explain why a good sync doesn't give an immediate throughput improvement.

[#5]

I think the highest speed we have ever had was about 5mbps and that was a one off.  Generally it sits around 4.5mbps.  Some of the drop outs just maybe because I changed the filter and also switched off the router and then rebooted it after having one or two earlier drops outs for no reason.