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I am a solicitor and will try and help. Do you have a lease? If so, what does it say about fixtures and fittings?
Yes, please upload a copy using the paperclip icon.
Usually, in commercial properties, tenants are responsible for such matters, unlike residential properties where the landlords are responsible.
You may try and negotiate with the council about meeting halfway if possible or them agreeing to waive the rent in lieu of you paying for a replacement boiler, as conversely, there is nothing in the lease/tenancy agreement that says the council has to replace the boiler.
All the best