Repeated ADSL dropouts and low speed

Question

I've drawn a blank here and I'm wondering if anyone has any suggestions?
Initially my connection was rated at somewhere between 7-10Mbps and it worked okay for just over a year at just shy of 10Mbps, but now I'm having problems.
A couple of weeks ago during the hot spell the connection kept repeated dropping, giving me a flashing broadband light on my homehub 3 Type A but the speed remained okay (about 7Mbps IIRC). Since then the drops have continued in bursts (sometimes it's okay for a day, other times it drops every few minutes for hours) and the speed has become increasingly worse to the point of barely usable.
Yesterday I was down to 4Mbps, today 2.5Mbps. Obviously I can't maintain a connection to gain an improved speed due to the dropouts.
I have the router connected directly to the master socket, I've tried a new filter, I've tried with and without the faceplate, I've checked the cable to the router and I've disconnected the phone and the sky box to rule those out. I've also left the router running with no devices connected to it whatsoever (wired or wireless) and it still loses its connection periodically. I can't think of anything external that would be affecting it that I've noticed, and I'm fairly confident I can rule out the weather because it's been going on longer than the current rainy spell.
The quiet line test gives me a very quiet line and calls are clean and clear when I phone people.
the latest stats taken from my homehub are:
Connection Information
Line state: Connected
Connection time: 0 days, 03:13:18 (note: This is due to a disconnection - I didn't powercycle the router)
Downstream: 2.997 Mbps
Upstream: 584 Kbps
ADSL Settings
VPI/VCI: 0/38
Type: PPPoA
Modulation: G.992.5 Annex A
Latency type: Interleaved
Noise margin (Down/Up): 19.5 dB / 18.7 dB
Line attenuation (Down/Up): 31.8 dB / 18.2 dB
Output power (Down/Up): 18.1 dBm / 9.9 dBm
FEC Events (Down/Up): 749108 / 60565
CRC Events (Down/Up): 6 / 811
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
HEC Events (Down/Up): 40 / 2174
Error Seconds (Local/Remote): 352 / 3180
and from the speedtest:
Download speed achieved during the test was ­ 2.51 Mbps
For your connection, the acceptable range of speeds is 1.2 Mbps­ - 4 Mbps.
IP Profile for your line is ­ 2.71 Mbps
Upload speed achieved during the test was ­ 0.46Mbps
Upstream Rate IP profile on your line is ­ 0.83 Mbps
Anything I might have missed? any suggestions?

Answer 1

Sorry if I caused any confusion there - this is the socket I have everything connected to (the only one in the house). previously it had a faceplate on it, but I removed that to see if it made any difference. It didn't.
The only thing that is currently connected is the homehub, via a filter. Previously a phone and a Sky+ box were connected, however I have disconnected them to see if it made any difference and only plugged the phone in for a couple of minutes to do the quiet line test.