How long should i wait for my boiler to be fixed by my landlord?

Ask the landlord which he would prefer. To deal with it himself or for you to arrange the repair and either bill him or deduct it from the rent. Remind him that he is required to maintain the heating by law. He should have issued you with a Gas Safety Certificate when you first moved in, so if he hasn't he is already in breach of the Regulations and could be facing a hefty fine. The Gas Safety Certificate has to be reissued each year too. Also all work on a gas appliance has to be carried out by a Gas Safe registered engineer. All the regs apply to ALL gas appliances in your accommodation, e.g. Cooker, Hob, gas fire.