As you have been together for many years you are unlikely to be on a fixed term contract for your rental property. You are highly likely to be on a rolling or periodic tenancy- find out. It's easier to end a rolling or periodic tenancy as you do not need your ex partner's agreement.
Information how to do this on England.shelter.org.uk. Speaking to your partner/landlord/rental agent of your intentions first stage. If your ex partner does not agree- the landlord/agent will contact her to ask her is she wishes to continue the tenancy on her won. If her answer is no, she can not afford to do so- they will communicate her options to her. This will also have the benefit of informing the landlord/agency of affordability and relationship breakdown problems that reduces confidence that the rent will continue to be paid on time. Thus the property owner will be informed and may wish to give notice on the tenancy themselves.
Your head may be telling you your ex partner is holding all the cards and therefore you will continue to be accepting of the situation albeit frustrated and depressed - but that is not the case. Assert your voice and make some choices and decisions - seek support from your family and/or Citizens Advice Bureaux if you need help.
Relatively new here so an introduction.

