I don't really know much about divorce legal mumbo jumbo, but if you listen to the guys, you should be fine Gavin.
Try to plan for every eventuality - imagine what 'evidence' she may come up with against you, and think of ways to disprove her evidence/refute her claims. Hearsay technically shouldn't be allowed in court, but it can help build up a profile of a person (Just like character witnesses can) A judge may take such evidence into consideration when making the final decision -if they believe it is relevant, so make sure any dirt you can dig up on her is good.
If you can think of any character witnesses that may go against you, try to sweeten them up a bit (Obviously this one will require caution coz it could backfire in court) 8O
Neighbours can be good witnesses, since they may have noticed any arguments you may have had with her recently. They may have even noticed patterns in your arguments (Ie. she started them) or they may simply think of you as a 'better parent'.
When you are in court, her lawyers will probably try to make you look incompetent, or try to confuse you so you end up damaging your own defense. Just keep calm and do some homework, and you'll be fine.
Remember, we'll be right behind you.
(It's a shame that my operatives can't help you, but of course, they can't interfere with the laws and justice system of another society

)