First Fixed Ride

I don't think this would have happened if you had relaxed your knees properly? Seems to me you are riding with very tense legs. And rest your body weight on your ass, not the soles of your feet.

It seemed to happen when I had just pushed down with my leg and as my pedal came up, I naturally locked my knee and tried to coast, so when the pedal came back up, I couldn't really bend my knee to accommodate.
Is this because of my technique or because of my seat height or something?

Out of interest, is the bike okay?

I got a nick on my new seat, but I got my glasspaper and wire wool out and the handlebars were as good as new. Fuck tape.

The constant pedal action nearly threw me straight out the saddle, i remember flying along with one leg strapped in, one waving in the air, bouncing up and down like a right twat.

Hahaha, its like your describing my first ride!