Plumbing question - smells

[SistersofPercy]

CoupeKid said:

Any conclusion?

There is! I went down this route:

SistersofPercy said:

Remove the dirgo, extend the pipe up and out of the front of the house.
Replace toilet seal.
Replace sink trap.

In the end decided to replace the toilet and sink with a built in vanity style unit to give me some storage as well and update the space a bit. Plumber was great, two days on the job, replaced shower trap again as well just to be certain. Boxing in didn't look anywhere near as bad as I was expecting and he managed to sort it without losing tiles.
So far it seems to have worked. Not a hint of a smell. Almost 100% sure it was caused by the boxing around the dirgo being to tight and stopping it moving as it should.