Hello I am a solicitor with over 15 years experience. I will try to help you with this.
The starting point here is to look at the lease and see what this says about who is responsible for paying for the upkeep of the space heater. If you can tell me what the lease says about this I will be able to give you a useful answer
Firstly under definitions it covers the 'heating' under the definition of demised premises but mentions nothing specific to the heating
Is ther anything more general. The heating is included as part of the demised premises you say, what does the lease say about who is responsible for maintaining the premises?
Us as the tenant and it says that we are to leave the premises in the same state as per the schedule of condition in the lease although we never used the heater
What, if anything, does the schedule say about the heating. What condition was the heater in when you moved in?
The schedule says nothing about the heater
OK I am not sure I will be able to give you a definitive answer here. You were responsible for maintaining the premises while you were renting them. There is nothing specific in the lease requiring you to maintain the heating but it is described as part of the demised premises which you were responsible for. You have never used the heater so do not know what sort of condition it was in when you moved it there. There was no specific requirement in the lease requiring you to have the heater serviced n a regular basis. I assume there were notices on the heating equipment or in the premises requiring periodic servicing. Is there anything in the lease about complying with CORGI servicing requirements or anything of that nature? I will assume not.
It seems to me that you have a good argument for saying that you are not responsible for paying for the heating to be serviced now that you have left. I take it he is not saying the heating is not working just that it is overdue a service. If the landlord did not make you aware of this requirement and it was not otherwise obvious then I think you are probably not responsible for the servicing. However, if the landlord is able to show (eg through a gas engineer’s report) that the condition of the heating has deteriorated on our wathc and that is why he needs to service it then you may be responsible. Do you know how much money this is?
You might think, assuming you do not need references from him, or want to return to the premises in the future, that you do not need to pay him. If he starts court proceedings to recover the money which would be in the small claims court (ie < £10,000) you could always settle to avoid judgement against you.
I hope this answer is helpful but please feel free to ask further questions.