Hello I am a solicitor with 20 years experience. I will try to answer your question.
If you have a tenancy you are in a contract situation that you can not legally break. Yuor own personal difficulties are irrelevant as far as contract law is concerned. AM I right in thinking you will have to leave the country soon, in any event before the end of the tenancy. How early will you need to end the tenancy and what is your rent?
OK, technically you will be in breach of contract but the landlord has a duty to minimise his loss. If you give him reasonable notice then with luck he will be able to find a new tenant to take over from you and incur no losses, He only has a right to claim compensation if he suffers a financial loss. If he has not yet started marketing it then this may well damage his claim as he is not trying to mitigate his loss.
If the heating system was not working and you had given the landlord notice of this then you will have a counterclaim to set against his for rent not in the final 3 months. Your counterclaim will be for less than the rent and will only set off a small amount of the rent.
If you are moving abroad it may well be that the landlord decides it is not worth pursuing any claim against you. So legally you may have a liability but practically your landlord may find it hard to take action against you.
Have you told him when you are going? Unless he agrees to waive the last 3 months rent then you will have the choice of paying him it all, negotiating a lesser payment or not paying any more and seeing what he does. I have discussed his options above.
You can't make him do anything you can either pay up (all or part) or leave and see what he does, hoping he will do nothing. If the landlord won't engage then these are your only options
There isn't much more I can add there is some uncertainty in your position unless and until the landlord gets involved.
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