WD40 is a water displacement product, The WD meaning water displacement. It does lubricate also but isn't a proper release product.
Plus gas is developers purely as a release product.
There is a large thread that agrees the use of each product.
http://forums.mg-rover.org/showthread.php?p=3926407Also if you had a blow torch you could concentrate heat on the lock rings only so that they expand leaving the inner shock and thread cool. Be carefull with flammable chemicals here.
The final option and I guess you've already tried it is to use an appropriate sized 'c' spanner holding it in the correct position and shock the ring with a mallet. Or fit a scaffold pole to the spanner and be strong.
