Thanks for that, the guy came out yesterday and said yes it was blocked and a part was broken, both of which he fixed, we are getting it drained too this week, and he siad this should sort it out. I mentioned the "breather" pipe and he said it was not required, the one at the house was sufficent. There is still a smell in the bathroom today, I'm hoping once it's drained, we will have no more smell - if not I'll be straight on to them again. By coincidence our neighbour was in last night and they have an "ecopure" treatment system and they are had the same problem last week. I think these systems are high maintainance and high cost!