As I said in the subject line this maybe of help to some.
For a while now my router (ZyXEL 660-P1) has been disconnecting my line an then coming back on and of course after doing a load of checks and reading the Forums I blame +Net, but I was wrong.
After two calls to Tech. support, the first one blamed BT and the second one solved my problem.
After a short power cut my Router reset itself but to the wrong comfiguration,
Service Type was showing PPPoE when it should have been PPPoA.
VPI set at 3 when it should have been 0 and
VCI set at 35 when it should have 38.
Correcting these errors my line now seems to be OK