I have had problems with my PlusNet ADSL ever since I bought it 2 years ago. At the time I had my original router modem replaced. But my connection would go through problems. The mode was always slow to synch. If I did anything to the telephone system it stood a chance of making things worse. When I first had it installed I had a BT engineer come and have a look at it. He admited that ADSL was new to him and all he did was connect a portable he had with his own modem and that worked fine. I even bought a new modem in the hope that it would solve my problems but it was worse that my original modem as it would not synch at all.
I tested both my modems in my neighbours house when he had ADSL installed and they both had no problems synch'ing.
Recently the problems got worse. I had one day when the mode did not connect for 2 days. I raised a ticket with the PlusNet support and a BT engineer visit was arranged.
The engineer arived and I described the probmes I had been having. He imidiately asked if I had a filter fitted. This turned out to be a filter fitted to stop radio interfearance on the telephone line and must have been installed before we bought the house (15 years ago). The filter was an RF2. The engineer said we could have an RF3 fitted that would be ADSL compatible but he recomended trying it without and that is what I opted for.
Now my ADSL works perfectly, with both my ADSL modems and the telephone is louder - who could ask for more.