They've basically given you your structure.
1* Discussion of Ireland and Burstow and the subsequent HoL decision and implications.
2* How and what this decision clarified in regard to the OAPA.
3* Despite the implications of 1), the ever-existing problems that exist within the OAPA and the need for reform.
By the way, Ireland and Burstow are two different cases in their original context but were addressed jointly by the HoL so you'll need to look again at the individual facts of each case.
I also wouldn't limit your discussion to Common Assault, these cases had far-reaching implications beyond one offence.