Since about Friday, I have had a horrible, loud, scratching noise on the phone line that makes it nearly impossible to hear people. At this point the internet was running fine.
I did isolation tests with different filters, phones and jack points, and concurred that the filters and phones were fine, but one of the jack points in the house was causing this issue. I have 2 jackpoints, the 1 in the lounge has the ADSL modem, and the one in the kitchen has a filter and cordless phone.
When any phones were plugged in with filter into the kitchen jack point, I had the horrible noise. In most cases only I can hear the noise and not the caller, but the caller can hear me absolutely fine.
When I unplugged the modem and plugged in a phone with filter into the lounge jackpoint, the phone calls were fine.
I would plug both phone and modem into the one jackpoint, but I don't have a double adapter.
Now as of last night, my internet speed has been dropping, to where it is now. (normally around 2.4Mb/s)

What would be causing all of this? Is it my internal wiring (house is about 3 or 4 years old), or is it the line to the house somewhere, or is it VF?
Any help would be great!