Just my two pennies worth, it looks like your line is perhaps suffering from external interferance if there is no electrical appliance within your property which is causing it.
Looking at your line stats, the only suggestion is to get back to BT and see if they can raise your downstream noise margin to see if it will make any difference in the evenings. Your stats show a figure of 4.4db. To check for the actual default noise margin on your line, you need to disconnect the ADSL cable for a few seconds and check the figure again after you have reconnected the cable and you have internet access. It is probably either 3db or perhaps 6db. The default values start at 3db and go upto 15db in 3db steps. The 'noisier' the line, the higher the value which should be automatically set by BT's systems.
Increasing the noise margin will reduce your maximum download speed btw.
If a higher value downstream noise margin does resolve the problem, sadly the value may not stick from my experience when I had ADSL. In the past, I've requested values as high as 9db, only to find it eventually drifted back down to unacceptably low 3db for my ADSL line leading to the return of occasional disconnects or slow speeds in the evenings.
You currently have ADSL2+. Another option is to request your line to be downgraded to ADSL2 only, this will set your maximum download speed to I think no more than 12mbps. The benefit will be a 'higher' default noise margin on your line.
