Any question answered...

if you already have an account/log in with easyjet and when logged in it offers you the option of printing your boarding pass does that automatically mean i've checked in?

i brought my passport into work thinking i'd at least have to put my passport number in. i can't see any option like that or anything else "check in" related. but i was able to print off boarding passes. is it like the passport number equivalent of wiggle knowing my debit card details?

and if so am i checked in?

Yes you are checked in. The airline aren't arsed about your passport, only airport security.

You still need your passport to board the plane/enter the departure lounge.