I reported this a while ago and a BT Engineer visited but could find no fault (Although after his visit my download, upload speeds doubled back to what they should be and my ping times dropped back to what they should be but the BT engineer said he hadn't adjusted anything).
However I'm still getting multiple disconnects every single day, indeed every single hour. This is the log from my router for this morning:
| 11:09:10 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 connected. |
| 11:09:06 08/02/2016 | System | Notice | DSL connection is active. |
| 11:08:38 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 disconnected.(ERROR_NO_CARRIER) |
| 11:08:38 08/02/2016 | System | Notice | DSL connection is disactive. |
| 10:48:33 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 connected. |
| 10:48:28 08/02/2016 | System | Notice | DSL connection is active. |
| 10:48:00 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 disconnected.(ERROR_NO_CARRIER) |
| 10:48:00 08/02/2016 | System | Notice | DSL connection is disactive. |
| 10:47:16 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 connected. |
| 10:47:11 08/02/2016 | System | Notice | DSL connection is active. |
| 10:46:44 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 disconnected.(ERROR_NO_CARRIER) |
| 10:46:44 08/02/2016 | System | Notice | DSL connection is disactive. |
| 04:21:50 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 connected. |
| 04:21:46 08/02/2016 | System | Notice | DSL connection is active. |
| 04:21:19 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 disconnected.(ERROR_NO_CARRIER) |
| 04:21:19 08/02/2016 | System | Notice | DSL connection is disactive. |
| 02:40:32 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 connected. |
| 02:40:28 08/02/2016 | System | Notice | DSL connection is active. |
| 02:40:01 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 disconnected.(ERROR_NO_CARRIER) |
| 02:40:01 08/02/2016 | System | Notice | DSL connection is disactive. |
| 02:39:22 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 connected. |
| 02:39:18 08/02/2016 | System | Notice | DSL connection is active. |
| 02:38:51 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 disconnected.(ERROR_NO_CARRIER) |
| 02:38:51 08/02/2016 | System | Notice | DSL connection is disactive. |
| 01:40:14 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 connected. |
| 01:40:10 08/02/2016 | System | Notice | DSL connection is active. |
| 01:39:42 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 disconnected.(ERROR_NO_CARRIER) |
| 01:39:42 08/02/2016 | System | Notice | DSL connection is disactive. |
| 01:37:31 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 connected. |
| 01:37:27 08/02/2016 | System | Notice | DSL connection is active. |
| 01:36:59 08/02/2016 | System | Notice | WAN connection INTERNET_TR069_R_VID_101:IPv4 disconnected.(ERROR_NO_CARRIER) |
| 01:36:59 08/02/2016 | System | Notice | DSL connection is disactive. |
So eight disconnects from 1:36am to 11:08am and each only for a few seconds.
When this happened before I was getting the same number of disconnects continually and then my speed started to drop. Normally I get around 32-38MB download and about 1.7-1.9MB upload with a ping of 26-32ms. Just before the BT engineer visited my download was down to 18MB, my upload was about 700kb and my ping could be as high as 2500ms.
As of right now my download speed is 37.3Mb, upload is 1.92Mb and ping is 31ms. So the quality is good....when it's there.