Actually I'm not sure it matters - if it's the last thing in the turn or the first thing in the turn, the effect is the same.
That would depend on what happens in the turn sequence.
If you charge and then pursue in one turn then what can you do the next turn?
Do you rally from pursuit in the movement phase. Or do you rally from pursuit in the compulsory move phase.
And if the pursuit is in the next turn then you do not get the big extra movement as described above.
E.g. I charge, pursue turn 1, Rally turn 2, Charge turn 3.
Or you charge turn 1, pursue turn 2, rally turn 3, charge turn 4.
Barry all you have is the charage declaration step before the compulsory move step. And the compulsory move step has charges and countercharges in it.
So declare charge on pursuers. They test? pass or fail decide what they do. Then move both units into contact. This may mean that the routing troops escape the pursuit. Note I always think that pursuers should move slightly slower than routers as the routers suddenly break and but usually the people already in combat stay a bit longer holding up the pursuers. (you could give the routers an auto casualty for this)
If you have the pursuit at the end then the careful charge that you set up to hit the pursuers could end up with watching them ride past. (of course you could allow units to wheel in a charge which means they might catch them Actually we allow charging and counter charging units to wheel, at half speed of course. And they must move 3" in a straight line to count charging.)