Tenants won't move out!

It's good that it's rent a room - removes tax as an issue.

That doesn't necessarily make them licensees though: Revenue and RTB have different rules, so a situation can be a rent-a-room tenancy.

And the heating is a concern: even licensees are supposed to be able to independently control their heating.

Sounds to me like this is a terraced house, with the living room (probably with a downstairs bathroom) turned into an apartment with a barrier between that room and the rest of the house.

OP uses the back door and the people in the "self contained" room use the front door. I doubt it is allowed to split your house in this way (fire regs for starters). So no way in hell can this be anything but a licensee situation.

When they go on holidays get a builder in to knock down the partition and put the house back as it was. Dump any kitchen, beds, carpet, furniture out of the room and clean up the mold issue. At the same time bag their stuff and leave it outside for them. Dont know what you do about your husband, but if there is/has been abuse involved, financial, bullying etc, there are places to go for help on that too.

It does appear to be laid out as you explained however if it was me personally I would ask a solicitor first. You could have people taking a case to the Rtb with a written rental contract and evidence that they had their own separate living accommodation.

It might be as you said a licensee situation but it might also be a costly mistake

Due to the divorce element of this, detailed legal advice is required and lots of the suggestions here are potentially illegal. Go consult your solicitor about this.