From Mental Health Law Online
Amongst other things, this Act makes provision for the prohibition of smoking in certain premises, places and vehicles. This includes enclosed or substantially enclosed areas of mental health units.
Smoke-free (Exemptions and Vehicles) Regulations 2007 which allowed for a temporary exemption for English mental health units until 28 July 2008.
Smoke-free Premises etc. (Wales) Regulations 2007 which allows for a permanent exemption for Welsh mental health units.