UK Landlord Forum / Life

Please help.  The rented space that is my shop is freezing!!  My landlord is proving very difficult and, as well as entering my shop when I'm not there, he has locked the back (fire exit) door from the other side, and turned off the power to the wall sockets, so that I have no means of heating the room.  I've become ill from the chill, and am losing customers because it's too cold inside the shop.  What are my rights, and what can I do?