Hi, Where can I find information about whether or not I need emergency lighting in a 4 bed HMO (in Wales) please? 

http://www.cieh.org/library/Knowledge/Housing/National_fire_safety_guidance_08.pdf  is the main guidance, but as it's a bit old some councils have produced updated guidance for their areas  so you should check the condition standards on the website for the council the property is located in.