Thank you for the additional information.
The difficulty you may find is that the energy company may argue that you received energy from them continuously for this period without raising a dispute. If it is that you did not wish for them to provide services to you, you or your wife would have been expected to contact them within a reasonable time of having moved into the property to notify them of this fact. By continuing to accept their services without notifying them that you did not wish to do so, you may be taking to have implicitly agreed to the contract.
You mentioned being of the view that this may have been included in your lease agreement. If this is in fact the case, then your grouse would be as against the landlord, to reimburse you for any monies you have had to pay to the energy company.
You may however ask the company to exercise their discretion in not requiring you to pay all the outstanding energy charge, in light of your previous ill health. I do believe this may however be discretionary.
You may opt to raise your concerns with the Energy Ombudsman to see whether they may be able to mediate on your behalf for some or all of the bill to be wiped of in the light of your ill health. I will provide the Ombudsman's details, although you may find that you may still be required to pay.
I am unfortunately obliged to give you accurate guidance even if it is not favourable.
I do hope I have sufficiently answered your query . I would be grateful for your rating at this stage by clicking on the row of green stars at the top of the screen. Feel free to send me your follow on questions after your rating, if you still require clarification, I will still be able to respond to you.