is it safe to turn my boiler off daily?

my boiler serves the main house and a small annexe attatched to the main house. the people renting the one bedroom annnexe have the heating on all day and all night, this resulting in a huge gas bill. the only way of my limiting the usage is switching the boiler off at the on/off/reset button on the boiler is this safe to do? its helped my gas bills. the boiler is a vokera mynute he.