I know some of my colleagues (past & 'present') that have been RAF-ATC previous to joining the civvie world.
However, as far as I'm aware, although you get an "RAF ATCO Licence" this isn't a licence one could use in the civil world. I believe that you have to sit the exams for the civil licence to get one, may be wrong though.
If your friend has been doing ATC in the RAF for the length of his/her service, I imagine it shouldn't be too much of a task to convert to our side of the barbed wire fence.
That said; RAF-ATC vs. [civil] ATC (I'm told) are very different games.
Good luck with whatever your friend ends up doing.
Traaaaaaaaaaa.
