Intermittent Line Fault and Speed

[#1]

Two weeks ago my speed dropped from a steady 11 Mbs to 5Mbs. This coincided with a lot of noise on the phone line which then ceased. Yesterday after having the router switched off for a week (as away) I had a speed of 11 Mbs again which dropped to 0.27 Mbs. Again this corresponded to a period of a great deal of noise on the phone line. I did a quiet line test using the test socket with a different corded phone and it was quiet then a short burst of noise then quiet again.  I reported a phone fault (with Plusnet) and the line tested OK. Today the line seems OK again. A BT engineer is booked for Wednesday.
As it seems to be an intermittent fault will I be charged If he can not find a fault?
Am I right in assuming this is the cause of the very slow broadband speeds? Is it possible to see a chart showing my broadband connections?
Router Stats.  Maximum Bandwidth (Up/Down) [kbps/kbps]: 888 / 12,668. Bandwidth (Up/Down) [kbps/kbps]: 440 / 287
                      Line Attenuation (Up/Down) [dB]: 15.5 / 29.5. SN Margin (Up/Down) [dB]: 23.0 / 20.0

[#2]

Hi Salmo.
I can see that you've got a engineer booked for Wednesday to fix your phone fault.
Let me know how you get on, it look's like this is the cause of your intermittent connection.

[#3]

Hi Chris
Engineer came out and could find no fault. Also said no fault on my side so hope I'm not charged! Line fault is intermittent and someone's law says it will be working perfectly when engineer calls. He said it could be a dodgy connection somewhere but as all his tests are OK he can't do anything else.
Speed still 0.24Mbs download on speedtest.net (which then gives it grade A  (better than 88% of GB!!!)). Hopefully this will increase in 72 hours if line stays stable
.
Line Stats are
Maximum Bandwidth (Up/Down) [kbps/kbps]: 888 / 13,296
Bandwidth (Up/Down) [kbps/kbps]: 440 / 287
Line Attenuation (Up/Down) [dB]: 15.5 / 29.5
SN Margin (Up/Down) [dB]: 28.5 / 19.0
Cheers Salmo

[#4]

Hi Salmo,
As it's still dropping I'd suggest running though the checks at http://faults.plus.net so we can get this raised as a broadband fault.