hi gtrx, im new on this as ive just bought a new skyline on wednesday, as to ur problem wiv the nut what ive done before is find a good socket that is a bit smaller than the nut and hammer it on, it should be really tight on, dont exspect to use the socket again as it will probably be damaged afterwards, will need new nut aswell, hope this helps.:clap:
try to get your hands on some "screw grab" or "Hammertite". Not sure what you call it up in the UK. It's a sticky paste/gum type thing that comes in a tube. Apply it to the inside of the head of the lock-nut, and then try to wedge in something (maybe like will robson described).
This should be left to dry for a few minutes. it forms a super-adhesive bond with the lock-nut. Then use a wrench to try and turn it out.
If this don't work, then drill into the lock-nut and try to wedge in something as described above.
Also spray in penetrating oil and let it soak a bit before trying to loosen.
Can try a water pump plier perhaps? might get lucky, you never know but chances are it is stuck in tight and, Off course, if you don't have the patience for all this you can just drill through the lock-nut.
You'll find it a fair bit easier if you use the 'smaller socket' route to heat the socket with a blow-torch/blow-lamp first, expanding it slightly. Then hammer it onto the offending nut, give it a minute or so to cool then remove said nut and socket. Likewise - the socket will be mostly screwed for any use other than removing similarly FUBAR'd locking wheelnuts