As I am sure you are aware, the men in the photo have just completed their basic training and won't yet have been assigned their trades. And so from here they are likely to have gone to all parts of the RAF, not only the well known Commands such as Fighter and Bomber Commands, but also communications, transport, avionics and weapons to name but a few. And if that wasn't going to make your task hard enough, all their service records are still with the MOD (RAF Disclosures Section, Room 221b Trenchard Hall, RAF Cranwell, Sleaford, Lincolnshire NG34 8HB).
On the plus side you can search Air 78 at the National Archives to find each man's RAF number, which is a major step along the way. You will need to register with TNA (it's free) to download the digital microfilm entries. If you don't know your father's number, you can start with that as you are more likely to identify him among the dozen or more Hoopers who joined up in 1937-38. The entries often contain the date of birth.
