Mine is cable yes but was pointing out router being in the loft and signal good.
Decent cable on ADSL should be ok - from the master socket.
you say that but i have to speak to people everyday who don't understand that "it worked yesterday" just isn't an excuse nor is it going to change the fact that your isp only needs to provide you with a powerful enough signal to get down a 1.5m max cable.
I did however used to have my router plugged into the non master socket and had little issue due to being with BE
