Now that the weather is cooler you have your chance. I am assuming your DH is not with you.
Do not turn on your heating, (or turn it off)
Stop heating the water for baths and showers. (boil the kettle for washing up), bathe or shower when they're out.
Do not do their washing or change their sheets.
Put on your vest and warm winter clothes and wrap a blanket round your knees as you watch TV in the evenings.
Hide any portable electric heaters etc.
Cook for yourself only and eat your evening meal before they return from work then sit watching the TV wrapped in your blanket.
Do not buy snacks or drinks that they can help themselves to.
Just make life for them as uncomfortable as you can (and you too I know, but we oldies are tough, and its a means to an end.)
When they eventually complain, show them your STATE pension amount, and say now that the govt has cut your benefits (even if you don't get benefits) and stopped your £300 winter fuel allowance you can no longer heat the house, or water for the house or afford to eat in the evenings.
BTW if you are on any benefits beware - by having them live with you, you payments may be reduced as it will be assumed they are contributing to expenses. You could lose benefits.