All employers have a "Duty of Care" under Health & Safety legislation.
Any employer that knowingly fails to inform employees that public transport is unavailable after a certain time due to weather conditions is guilty of failing to provide this duty of care. It does not end when the employee "clocks off". It is the employers duty to release staff reliant upon public transport in good time to enable those staff to travel home via public transport. All employers are duty bound to make enquiries if it is reported to them that "the buses are going off" and if this is confirmed then they must release staff. They are not however duty bound to pay staff that finish early.
Too many people do not know their rights under employment law in this country yet spend hours reading facebook !