En-suite plumping? I have a Air Admittance Valve (AAV) on my soil stack surrounded...

I have a Air Admittance Valve (AAV) on my soil stack surrounded by the loft cavity from my ensuite. A few weeks a go the wastelands (toilet, sink, shower) started draining slowly and when i flushed the toilet it drained very slow and next a gurgling sound be coming from the other plug holes.

A friend said that its probably the AAV getting stuck so no air be being permit into the soil system. I have a short time ago replaced the AAV and the problem is still happening.

Has anyone get any ideas to what else could be wrong?
Lawnmower running funny!?
Answers:    own you checked any manholes ...sounds to me like a blocked drain...could be a blockage contained by your soil stack pipe
Where is the best place to buy an...
I think you worthless your money getting a new spout. It all sounds approaching you have a partial blockage surrounded by the drain