WD-40 will displace any water in there and nothing more.
Step up to the big leagues and get some PB Blaster penetrating lubricant. If that or a similar product doesn't get things loose your last resort would be to carefully dribble some brake fluid in where the axle is seized to the adapter. This may eat your bearing seals and will destroy any paint it comes in contact with so be SUPER careful...but it will work.
I had the same thing happen to me . The solution was to tie-wrap the legs of the forks together very tightly so that as you unwind the axle is does not splay the fork legs apart. I also had to tap the axle with a rubber mallet to initially break the bond between the axle and the hub . Be bery careful that you do not impart to much strain to the crown therefore ensure that you secure the fork legs together as tightly as possible. Good luck and use plenty of rust breaker/ penetrant.
Cheers for all your help guys, I managed to get it off with a mixture of various different oils and lubricants and by also tie wrapping the legs of the forks.
I've defiantly got a duff axle though, I've tried it on 3 different wheels and on two different pairs of 36's and it gets stuck every time even if I put it in coated in greese.