Bad smell around bathroom

Well, I looked down the plug hole and saw no water just an elbow fitting so I thought mmm...
I cut out a section of bath panel tiles on the other end behind the bin (2 sides tiled) and stuck my head and torch under the bath and saw the bath waste had a fanny trap on with the knuckle elbow so I thought right that's it. I said it will be blocked with hair and not fully closing.

I returned in a weeks time to slice into the main side of the bath panel and to fit one of those all in one trap/waste Mcalpine jobbies as the old waste was broken anyway and I examined the fanny trap to see hair but not as much as I expected and the lips were more or less closed  .

Got the water running and tested for leaks and then looked to the outside wall to see a dirty great 1 1/2" lead pipe hanging out of the wall open ended, I thought surely not and I looked out of the window at the stack and it had two lead waste pipes cemented into a cast iron Y junction but the bath and the basin were only sharing one and the other one was venting under the bath. The main stack even had a Durgo on top from when some guys last year put a shower room upstairs.

I capped it off outside and tested all the toilets and they were okay. The smell had driven her crazy for 2 years since she moved and and came and went apparantly, it makes sense now it was worse in the cupboard as the smell was going under the floor.