Good. Sounds like you're getting nearer mate.
'Timed' drop-outs
really can only be 1 of 2 things as the engineers have said. Either faulty DSL equipment in the exchange/ Fibre Cabinet (Lift & Shift), or REIN.
Don't know if you've read other threads on REIN, but you could use a portable radio set on the AM/MW range and tuned into 612Khz frequency. Then, at about 10am have a walk around your house and see if there's any evidence of REIN. You'll know it when you hear it, as in a REIN-free zone its relatively quiet on the radio, just background 'hissing', but when its prevalent the noise level goes up a lot. Put the radio next to your electrical meter and you should get an idea what it will sound like.
I'll be honest and say, I'd be surprised if the engineers get a REIN visit before a Lift and Shift is attempted. Its part of the protocol we have to adhere to on the crib sheet. REIN engineers will only usually attend if we have done a
L&S,D-side change,E-side change,Fitted new NTE5,Fitted a RF3 filter, Fitted a NTE2000. I've not had call to get them out recently, so not sure if the process is still the same.
Anyhows, best of luck with it.