No CCTV footage provided that shows her leaving her home that day. With no signs of a struggle in the home it just appears to be that whatever happened was between home and work that morning. We have footage of the day before on her walk home so the lack of footage going to work concerns me somewhat. (As you stated it might have been held back by LE.) The alleyway camera is to the north of her home, I believe, and she walked south to work. So that camera isn't going to capture her if she walks out the front door.
The walk to work doesn't sound like her normal commute given her car was in the shop. If it wasn't in the shop that long it almost seems like a crime of opportunity (stranger).
I don't know what to think of alleyman. Yes, did act suspicious by stopping when someone crossed his path and I understand LE wanting to find him. But I also wonder if he is completely unrelated to the disappearance. Why not come forward? He is a criminal - casing houses, drug dealer - and always avoids contact with LE because LE would, of course, want to know why he was there to begin with? Speaking of withheld footage, could LE have other footage of this guy in the area previously and acting in a similar suspicious manner?
Tough for me to follow this without the benefit of local or UK news. That is one reason why I only follow about 3 or 4 cases outside the USA.