They are. I found that Stations are in AIR28 and misc units are under AIR29
But it is very likely that these the ORB of a particular station is split over different files depending on the status of the station. For example, If I wanted the history of RAF Peshawar, I need to consult four different files spread over AIR28 and AIR29. i.e when Peshawar was a standalone station it was under AIR28 and for the period there was a OTU there, it is under AIR29
For Sutton Bridge, this is a good place to start
http://www.nationalarchives.gov.uk/c...accessmethod=0 It ends in 1940 as the ORB pages from 1940 may be under another file - say if the CGS was established, it may continue in the CGS' file.
The next part may be in this
http://www.nationalarchives.gov.uk/c...accessmethod=0