I've been receiving a number of emails requesting how someone may go about researching a member of their family who was an air raid warden or in other ARP and Civil Defence services. The key starting point is their local archive usually at the library (or sometimes called a local history centre, local studies centre or archives centre). The online starting point would be the 'Search local archives' website.
However, I have searched through a number of these in the London area and details about an individual who may have served are generally absent. Unless they were a senior member (along the lines of an Incident Officer) then it's unfortunately highly unlikely the archive will have much more detail than their name appearing on a list of wardens (but even that is difficult to come across).
Finding details about an individual at these archives is therefore generally not going to happen. The archives do hold minutes of council meetings and some have letters from individuals but overall finding out about one person will not be possible. A few archives may have lists of wardens and the post they occupied but I have only seen one such list so far and it was for just a period in the summer of 1941.
Some areas do have active local history groups that can assist research but again the likelihood of finding any detailed information on one person is unlikely.
There is also the National Archives but their search engine often directs a user to the local archive. They hold numerous ARP and Civil Defence records but these are generally related to governmental business.
News about interesting insignia, ARP related info and period photos that turn up.