Thanks Zooker -- and topdrop. As Zooker said, whatever 'it' is you have to give it a name so you can identify it. The question really was with regards to the SID letters -- and the fact that for 'B' and 'C' departures for any SIDs out of Luton, the B or C identifies it as being a Luton departure, D and E identify it as being Birmingham and so on -- whether being able to identify like that was deliberate or just a coincidence.
To put it another way, if Brum had a CPT 1A departure, could Luton have a CPT 1A as well? (I can't help feeling I'm starting to answer my own question, because I wouldn't have thought you'd do that.)
I'm sure it doesn't work for the entire UK, after all there are more than 13 runways with SIDs (that's assuming we used all 26 letters which I guess we don't anyway). So you'd have to work out groups of airfields that shared common SID endpoints and assign letters to runways within that group. I guess.
Cheers
