Eastern Airways or whatever they are called these days (R/T "Eastflight") have to be the main culprits for this. Can make a Pennine session very "interesting" <img src="tongue.gif" border="0">
A polite "We'll use full callsign from now" should easily do the trick.
I'm not too big to accept we're sometimes wrong.
Not me persoanlly though obviously <img src="tongue.gif" border="0">