We dealt with this a year ago, but the question still comes up.
Very recently an employee of a client stayed at home because she was afraid to drive in snowy conditions. She asked if she would be paid.
The legal position is remarkably simple. If the workplace is kept open and employees are simply unable to get to work, the employer is not obliged to pay them.
However, if the employer decides to close the workplace, perhaps on grounds of health & safety, he will be obliged to pay because he has denied the employees the opportunity to work (regardless of whether they could or would have got to work).
Whether to allow employees to take time absent as holiday, unpaid absence or pay normally on the basis of time to be made up later (so long as this is confirmed in writing by the employee) is the employer’s decision to make.