Bouncing in my seat

Assuming the bike is set up ok how long do you reckon it would take to develop a reasonably proper pedaling technique? Being a lanky unfit IT geek doesn't help.

I shall await my flaming now...

Hard to say, but shouldn't really take too long - but you should be riding a gear that allows a cadence of 90 - 100, say 42-18 something around there.

I don't think being lanky or unfit should make a diff. You will get fit, and as long as you have your pedals and cleats (if you have them) adjusted correctly, your height should not a difference.