I did the BA Flight Safety Awareness course a couple of years ago (well worth it if you are UK based)
http://www.britishairways.com/en-gb/...fety-awareness
The over- wing doors on a mid haul are actually very easy to open but it seems that there is a difference in procedure.
The BA instructions are for the exit door to be thrown out the hole you just created as it will impede the exit of those behind you. Apparently in the US the advice is to leave it in the plane.