If there is no break clause which applies in these circumstances, then if you leave you are responsible for the rent until the end of the term or until the landlord finds a new tenant. He is under a duty to mitigate his loss to try to find a new tenant.
You may have a potential cause of action against the landlord if the landlord is the landlord of the flat with these obnoxious occupiers. However if your landlord does not only of the slat, then he is obviously not responsible for it.
They are not able to charge you all the costs they charge. They can charge you a reasonable admin fee. They cannot charge checking costs.
They are prohibited by the Tenant Fees Act: https://www.gov.uk/government/collections/tenant-fees-act
you already have my comments about them charging rent until the end of the term.
The tenancy comes up to its 12 month anniversary in a couple of days. Was it for 12 months, or did you renew it?
I hear what they say about the Business Break Clause, it would depend whether it actually said that it had to be with the same companies
in respect of the Business Break clause, from the wording you have given me, it does quite clearly refer to the transfer being by the same employer. And it would need to be more than 30 miles away.
Can I clarify anything else for you?
Please note that my answer is based strictly on the information that you have given me. If you have not given me all the information, then my answer may be incomplete or wrong.
I am happy to answer any specific points arising from this.
If you still need any points clarifying, I will be happy to reply because the thread does not close.