Nasty bathroom smell

[pandaman]

I have read previous posts on bad smells, not sure where the bad drain smell, (I think), is coming from in our bathroom. House was built in 1995 and we have been here since then. This has not happened before. Smell is just in bathroom, en suite shower room is next door but no smell there. Cannot detect any smell from sink drain or under bath, took panel off to check, no smell from toilet or cistern. Pipes from loo goes into a small boxed in area, took top off but all dry inside, loo waste goes under the floorboards as does the sin and bath waste. In shower room pipe from sink and loo go into a bigger boxed area, see photos, but not sure if they also go under the floor inside the box, all drain into an internal boxed in pipe in corner of shower room next to outside wall and downstairs loo and small sink also drain into that. There are no outside pipes visible. The bathroom loo, sink and bath all drain ok.
Are there any companies that have fibre optic gear that will work inside
I know they can do outside drains with drain scans and the like but not sure if they can do inside scans. This only started in the last weekend's week. Not sure what to next. Any advice welcome. 1st 2 photos are bathroom, other 3 are boxed area in shower room.

 

[blup]

Could be a loose seal in the shower room toilet, either at the wc itself or where it meets the soil pipe connection further along. The smell may be less prominent because its tiled in not boxed.

 

[Hugh Jaleak]

Do the simple things first, check manholes outside, see if any signs of a blockage, get someone to flush the WC's, and see if the water gets to the chamber. Check inside for air admittance valves, they can and do stick open, letting odours out. Shower? Check trap is full of water.