A landlord cannot turn off the heat on tenants.
A landlord has to supply heating equipment all the time. Its up to you to use them and pay for the energy supply. If the supply has to be switched off for repairs [gas] then other types of heaters should be offered to you,or you can request some. If you live in a property where the heating is part of a larger circuit which is controlled by your landlord ,he should inform you when this source is being turned off and an other source should be offered. If he/she just turns a supply of when they feel like it then they are breaching your civil liberties