I've had this piece on my mind for weeks. I'm certain that I've heard it lots of times on Classic FM or Radio 3, but haven't found anyone who can identify it. Very probably as soon as someone does name it I'll go 'duh!'.
I've created it as a Noteworthy file and saved as audio, with clarinet as the main tune and bassoon as an approximation to a bass harmony (it does something like that).
Which illustrates the point made by osewalrus recently, that you don't have to know everything, knowing where to find it is just as good (and often more useful, as the referenced information may be more up to date or contain further links).