This brings back memories of my disastrous trip last year from CDG-LHR, as some of you may remember. I was even more stupid than you, flyingquack.
I was booked to fly with bmi home. bmi cancelled my flight and rebooked me on BA, the last flight to LHR. I turned up at the BA check-in desk in T2B less than an hour before my flight only to be told I hadn't collected my paper ticket - bmi had informed me that I needed to collect my ticket from their ticket desk in T1 but I had completely forgotten. There was no way I could get to T1 and back in time to make the flight. So I was stuck at the airport overnight.
Luckily bmi put me up overnight and fed me but I still felt a right fool.