You're right those nuts can be tw@s Plenty of penetration fluid for a few days before you start. I also used a thing called 'Freeze your nuts off' 'tho can't say if it made a difference! I ended up having to hammer a size too small socket onto 3 of mine. You have to really give it some welly and get it all the way on (you then can get the nut out of it with a screwdriver and hammer - I used a vice on my bench) then on one I used a massive long piece of scaffolding over my breaker bar, the others I lifted the car as high as possible, then wedged the breaker bar onto the socket and between that and some bricks, then lowered the car on the jack and let the weight of the car break the nut off. Once you have just broken that initial crack then they come off OK. It's a right annoying old job but you just have to keep your patience, they will come off eventually