I know EXACTLY how you felt wsmempson, been there - fortunately still have the t-shirt!
It's that horrible feeling of your brains just dribbling down your back, leaving a cold, clammy, empty feeling in your head!
I remember one such occasion near Potter's Bar en-route Duxford when I suddenly had a "Where t f am I" moment - all I could see was very similar-looking motorways in every conceivable direction! By the time I had done an orbit to try to check position I was totally disorientated and had completely lost the plot, despite having GPS (with which I was not familiar), and 2 x VORs tuned in.
I called up Luton Radar (as I was listening on their frequency anyway - and the ability to do something as complicated as change frequencies was way beyond me) and told them that I was "Uncertain of Position". My mind was so gummed up that when they asked me for an approximate position the words that came out were "North of London".
Turned out I was still smack on track, just SE of Panshanger, NE of BPK.
No further problems after that, but I learnt a lesson about just how quickly you can become overwhelmed with even a trivial workload if something goes amiss in the air.
I don't even want to think about instrument flying!
SD