Its dodgy territory when they are, as you say, old, storage heaters. They can contain asbestos and they are within their rights not to work on them.
However, since two have broken at once, it points to a fault away from the heaters.
Could you upload a photo of your storage heater fusebox, and the meter aand surrounding equipment? We need to know how the incoming is wired and what the supply arrangements are to the heaters. It could be a supply company fault.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local