Sunday midday ish, there was a major leak on the south circular near Horniman (the same kind of area that bursts every few months - presumably a major weak area in the network as they seem to be forever patching up). Hole dug in the road, water pouring out and flowing down the hill towards the Grove Tavern junction. I assume that could be affecting Canonbie Road area.

I can't really comment on TW's 'efficiency' at dealing with these kinds of issue, other than to say it doesn't sound surprising. If you're on twitter you could try chasing them there. Public shaming may be more effective at getting some kind of update.