Do we know what area in East Sussex the arrest was made? I am in Hastings and previously lived in Eastbourne.
I'm so stuck on the motivation. Completely random attacks do occur of course, but imo that would usually tie in with mugging, a fight, or sexual assault.
The fact that he attacked her shortly after she left her home, could suggest premeditation to me. Lying in wait for her to leave the home. This would indicate they knew each other, or he was a stalker. I'd be interested to know her movements earlier in the day. Could she have been chatting to a stranger and mentioned she was excited to head out for a date later?
If premeditated, it seems unusual to use a can of drink (or something similar) for a weapon. Although easily disposed of, it's an unusual choice, and could give unreliable results. The carrying of her body into a park and covering with leaves is also strange to me. So many unknowns.