Thanks for the thoughts. I am convinced that there is some external cause of my ADSL problems because the difficulties seem to coincide with working days (we are retired so our daily domestic routine is uniformly the same, bath on Friday nights, etc.). I use an ADSLNation filtered faceplate but the cable plant in my house is probably OK as I have previously verified by connecting a BT Voyager 2100 direct to the master socket (with Exelcus microfilter) and observing SNMR intermittently and momentarily dropping to zero with the aid of DMT v8.07.
Being a tweaky geeky I will do the DG834GT Sky thing. That sort of thing appeals to me. Thanks Frosty.
My SAR130 continues to work with solid reliability, plodding away at a steady 4 MBPS. Let's see what wonders will transpire on Monday.