Sorted out the issue. Don't I feel a dumbass!
There were 2 more bolts in the sump at the back near the bell housing slightly recessed in the sump vents. These are much longer than the other 10 going vertical and not the 2 thicker bolts into the bell housing. So in total there are 16 bolts!
It all looks obvious now, especially examining the gaskets noticing there were 2 more holes but as the car is on ramps and axle stands I didn't get directly under the car to notice these 2 hidden bolts, simply working from the floor but to either side.
Thank heavens I stopped myself using more force trying to lever it as if the sump broke I would have been gutted as I believe these sumps are like gold dust!