Can anybody help please I'm trying to undo the crank pulley, can anyone tell a way to lock it so I can undo the nut? I have the head off at the moment. Cheers

they are super super tight.

put car in gear, get someone to press the brake (really hard!). Then undo the crank pulley. But i warn you they are silly tight, when i did this i had to use some extension bars on a socket so i could use a 2ft breaker bar resting on an axle stand to get the leverage to undo it. An impact driver would prob get it out easily but i don't have one so thats what i did.