Firstly, send it next day recorded delivery.
I sent all my stuff off with a letter telling them it would be great if they could do it ASAP as I was going on holiday and needed my passport back. Seemed to work... posted it Monday morning, got it back Friday morning! Needless to say I almost fainted!
I too heard they won't issue same-day any more. Bloody cheek if you ask me considering you're paying them £160 for the privilege of shuffling a couple of bits of paper, printing a license out, and pulling a nasty brown license wallet out of a box under their desk.
As for the "license in hand" thing, a friend of mine down south got signed off by his school's CFI (a rather big school incidentily) to take his girlfriend up an hour after passing his skills test.