Bathroom extractor fans lead to seemingly nowhere?

Excuse my very crude drawing, but I am trying to figure out where on earth these bathroom extractor fans are extracting to.

I live on the ground floor of a 3 story Victorian Town House in London. It has obviously been heavily renovated over the last 40 years as it has been turned into 5 separate apartments. Ours has had these bathrooms put in, and after dealing with some nasty damp in the two bedrooms; I've been keen to find out where these vents are going.

I've tried buying a cheap ednoscopic camera and poking it throught the ducting, but it only goes about 2 feets before I'm unable to tell which way it's going and the whole thing is so full of dust it's impossible to see much.

Does anyone have any tips on figuring out where these go, as I'm worried they just go into the ceiling cavity between the fake ceiling and the floor above, or into the wall cavity, leading more problems in the future.

https://preview.redd.it/e1iagjwgsv1e1.jpg?width=1940&format=pjpg&auto=webp&s=b03808d4ef5421bc4604968ec4d370b20bd7d35e

Here is also a look at the external wall, which is the alleyway between ours and the next house. Theres no external holes at all that can be seen.

https://preview.redd.it/sy1o015ctv1e1.jpg?width=480&format=pjpg&auto=webp&s=dbb3459eb39d54404331b025f38aec5ac57dbcb5

Weirdly there are 3 holes in the wall at the rear of the building, 1 of which I think goes into our hallway ventilation unit, and possibly the other two are for the two airconditioning units.

https://preview.redd.it/zsr8ueyltv1e1.jpg?width=480&format=pjpg&auto=webp&s=c3e5dd99fea251907fad87633ef920ff262e75a5

Thanks in advance!