Partner is working in sub 10 degree temperatures indoors and her emplyers are not doing anything about it.

Works in a small shopping centre in the North of England. Her shop doesn't have a front door just a big wide open area into the whole shop and the heating is broken. They have been told it's too expensive to repair and 'the cold spell doesn't last long'. (Even though this is the third year and predictably the cold returns each winter). She has also been told to remove the small fan heater as it's a safety risk.

I have looked it up and although it says there is no legal temperature it also says 16 is recommended and the employer has a 'duty of care' Is anyone able to help elaborate on how the duty of care is enforced? Is it just tough luck and deal with it or can they be forced into action?