Disconnections and Speed Issues.

Question

To start off, our BT Internet connection has been fine for years, not a problem at all, speeds weren't high, but they were modest and certainly enough for my needs, and there weren't really any major problems, just the occasional maintenance work interfering with it and other minor things...
Until the past 6 months that is, it happened it seemed for an alternating monthly period, on and off the quality would just drop ridiculously.
There would be disconnects and <1Mbps speeds (is that even broadband?), and just where we got to the point where we were going to call up, suddenly it would go back and become even better.
Sometimes going as high as 18Mbps which was unheard of for our area, until it crashed down again, this cycle happened until just over a month ago when it got a lot worse.
It started off the internet would disconnect and reconnect at a random speed, ranging from really low, to modestly high, and then a new symptom came into play, everytime a device connected to the router, the router would drop the connection and try reconnecting, it wasn't random anymore, we now know when it's going to disconnect.
Everytime my brother walks into the house with his smartphone automatically seeking our wireless connection, it drops.
Everytime someone powers up a PC that's on a wired connection, you guessed it! It drops the connection
Far more annoyingly though, everytime someone walks past the house and connects to our BT FON source, it drops (which I'd like to point out, at the time we had a Home Hub 1.0 and the BT FON was automatically always on and couldn't be disabled, a nice feature for our problem -_-)
We called up the technicians after this started, and they tried to diagnose the problem, and I use the word tried loosely.
Instructions were basically unplug the internet, plug it back in, and change the filter.
We did manage to wrangle a BT Home Hub 3 into our hands though, the morning it arrived we cradled our saviour, delicately placing it on the desk top, preparing to worship it's blessing of providing us with hassle-free internet at last..
But it was not to be, set it up, everything fine! Brother walks in from work.. and I'm sure you know how the rest goes..   
Humourous thing is, it came with a letter from BT saying we're on the up to such and such package (I think it was up to 20mb), it says our average speed should be 12mbps, but we've sat on pretty solidly for the past month 1.5mbps, it's been lower, but I don't think it's been higher...
We've tried the BT Help Phone Lines, they can't seem to help us, so I'm putting this puzzle to a wider audience of people who may have had past experience.
The only theory we have is that it was a BT mistake that they haven't realised, my father saying he saw workmen from BT working on the telephone pylon in our alleyway.
I'd ask our neighbours if they have any problems, but I don't want to get burgled if they find out we can afford internet...
I hope some people on here may be able to shed some insight or advice with how to tackle this problem, I'll say right now, we're paying something like £30 a month (maybe more, I don't get to see the bills) for an internet connection I could buy from a smaller company for £2 a month (1.2mbps average in the past month) 
Thanks in advance, Mike.

Answer 1

Test1 comprises of two tests
1. Best Effort Test:  -provides background information.
Download  Speed
1821 Kbps
0 Kbps
2000 Kbps
Max Achievable Speed
 Download speedachieved during the test was - 1821 Kbps
 For your connection, the acceptable range of speeds is 800-2000 Kbps.
 Additional Information:
 Your DSL Connection Rate :2264 Kbps(DOWN-STREAM), 1127 Kbps(UP-STREAM)
 IP Profile for your line is - 1997 Kbps
2. Upstream Test:  -provides background information.
Upload Speed
864 Kbps
0 Kbps
1127 Kbps
Max Achievable Speed
>Upload speed achieved during the test was - 864 Kbps
 Additional Information:
 Upstream Rate IP profile on your line is - 1127 Kbps
Installed a different browser on my machine for this test, internet speed has changed so I'll post an updated version of the router details
ADSL Line Status
Connection Information
Line state:
Connected
Connection time:
0 days, 00:45:53
Downstream:
2.212 Mbps
Upstream:
1.101 Mbps
ADSL Settings
VPI/VCI:
0/38
Type:
PPPoA
Modulation:
G.992.5 Annex A
Latency type:
Interleaved
Noise margin (Down/Up):
31.1 dB / 6.5 dB
Line attenuation (Down/Up):
24.3 dB / 13.5 dB
Output power (Down/Up):
13.8 dBm / 11.4 dBm
FEC Events (Down/Up):
0 / 0
CRC Events (Down/Up):
42 / 74
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):
38 / 53
Error Seconds (Local/Remote):
200 / 63