OK, Engineer arrived around 3pm at my mates (can't remember exactly) took one look at the Teryon modem and said "That's your problem"!
Apparently these Teryons can't handle the new QAM signal NTL are using since about a week ago and are refusing the config file or something like that.
So the modem was swapped for a new NTL 250 and the power level dropped via a 6dB attenuator as this was too high also, something I suspected all along!, it's now about 4dB.
So now everything is up and running and seems OK so far, the Engineer was an extremely nice chap who knew what he was doing

big thumbs up to him

.
Now he can play FFXI without disconnecting and crap like that!