Since April the term `residency' doesn't apply but I presume that was his original application. Now court orders can (but not all do) contain a line about who the child lives with.
In reality this means very little and it's just a label. It's got nothing to do with quantum of time either.
In terms of what will happen in a final hearing however:
When you get there you will have a chance to discuss things with your ex's barrister to see if you can come to an agreement. This happens quite often and if it does a draft order will be drawn up that is then submitted to the court. You'll go in and the judge will go through it to make sure it is OK and then ask if you have any thoughts on it. If you agree, it's stamped and that's it.
If you don't agree on everything (and remember...it's not an `all or nothing proposition' you may agree on some but not all points) it will go to trial.
Cross examination is part of it. You will have the opportunity to cross examine your ex, the CAFCASS officer and any other witnesses who have submitted evidence. Your ex's barrister will cross examine you and other people.
You mention a position statement. Practice Direction requires a bundle for a final hearing. A bundle contains all the evidence you wish to rely on and is used in cross examination. For example - if you wish to demonstrate that your ex, etc. has done something supporting documents can help a great deal as it turns it from a `he said, she said' situation to something you can prove and demonstrate inconsistencies in the other party's argument in court.
You've likely been asked to submit a position statement because bundles can be very involved but it may be worth assisting the court (and your case!) and putting something together. Google Practice Direction 27A for information on what you need to do!
In my experience as a McKenzie Friend it is seriously worth considering taking someone with you. A contested hearing is about as intense as it gets and it can be stressful. Even if you're strongest, sharpest and level-headed person in the world you cannot pay attention to everything and take notes!
If you need a few pointers, give me a shout!