divorce settlement

[marabout]

my ex has a 20% share of my home,when (a) sold (b) my death (c) my remarriage (d) cesstation of full time education of our son...our son is at present in his last year of A levels,my ex says that i must buy him out the day our son finishes his A levels,not before,or after. i wish to buy him out now,but,ex says no! when is the end of full-time education...A levels or university? my sons teacher says university.he also says that the court order for maintenance,ends when the A levels end...i was told..at the end of full time education.....help! what is it?..my ex pays 22 a week maintenance at present....