Hi MikeyB
Glad to hear you are not having the same probs as I am its been a right royal pain.
The engineer told me that there is a problem in the SN3 area of swindon
as the callout rate for modem problems has increased some 10 fold.
So far so good on a fix my signal was weak so he has boosted it from the box in the street and put in an attenuator (I think) its a filter of sorts lol
Its now a matter of waiting to see if it goes off again.