A couple of years ago I was very pleased that I was suitably prepared for VFR. IFR departure from Calais, inbound to Cambridge. Flight planned IFR all the way. Normal IFR departure clearance from Calais, and a handover to London. London weren't expecting me and couldn't accept me due to traffic density. Interesting couple of minutes ensued:
"Remain clear of controlled airspace and continue VFR"
"I'm in controlled airspace, and I'm IMC"
"Roger, descend immediately. Call VMC below, and clear of controlled airspace"
Fortunately I was VMC before reaching SALT. Then a mad scrabble to get a suitable VFR chart out of my bag and decide how to route to Cambridge. Solo at the time, so quite a handful.