To follow up on this, I tried re opting out and it didn't work. So I tried opting back in, waited 48 hours then re opted out, hoping it would 'refresh' the whole thing & disable it. It's now been a further 48 hours and it's still active.
Can anyone recommend anything?
There is one surefire method of stopping it, get a third party router. Depends how much you are bothered by it.