The front door was the only escape route. The apartment has very strong burglar proofing and according to testimony the sliding door onto the balcony was checked and found locked by the police. The balcony faces the parking area, and is quite high, so it is an unlikely escape route, even if the balcony door was open.
The front door opens onto a passage type balcony that is quite well hidden from the parking area and you do not have to leave the building via the main entrance, but can easily get to a car that is parked at the top end of the building without being noticed by many (if any) people.
The particular apartment was(still is) at the end of a long building with units 17 - 24 of the complex. There were no shadeports at the time. The only open field is the bit next to the R44 road and anyone climbing that fence during daytime would have been highly visible - I have aerial photographs of the area at that time.
Those of you with an honest interest in solving the case can contact me at firstname.lastname@example.org
and we will find a way of sharing some of the evidence from the court case and some other bits & pieces we have collected. I will not identify you to anyone other than the people who work with me on this. This offer is only for people who can show that they are willing to contribute positively and not just to satisfy curiosity eg. contributors to this discussion.