I have not been able to sleep tonight, and starting running through this case again and have come to the following conclusions (on the basis that they are the most likely IMO);
1) Corrie left the horseshoe area in a car having waited for a pre-arranged meet.
2) They were disturbed, or decided to move on - whichever it was they drove off in the direction that the bin lorry ultimately travelled (I think any connection to the bin lorry is a coincidence). Corrie's phone was possibly low on power given his usage that evening (or was switched off) and disconnected from the network in the BM area whilst still in the possession of Corrie or the person he met which is why it has never been traced.
3) The police have traced the cars/drivers which were in the horseshoe area at the relevant time, and given the lack of publicity, one of them is of interest and they are pursuing lines of inquiry which have come out of interviews. Without going into any detail (and completely unrelated to this case/area), as part of my previous job I was privy to information on Police investigations, and was frequently amazed at what appears in the media versus the reality of the investigation. I think in this case, the fact there is little or no information in the public domain is potentially instructive. I may well be completely wrong, and the lack of leaks from the Police is certainly unusual, although the MSM may be aware that what they know could prejudice the investigation and have decided not to make it public.
ETA - I've just spent some time watching the last CCTV in slow motion, and may have slightly changed my mind in that it's a possibility it wasn't a pre-arranged meet, or if it was Corrie expected the vehicle or person to be in Short-Brackland, which is why he was walking down that side of the lane - from his body language it looks like he didn't quiet expect whatever it was to be in the Horseshoe area, then checks to make sure he doesn't recognise anybody in the lane as he moves towards whatever it is. I still think the most likely thing that drew him to that area was through a location based app for arranging a meet.
Even in the Police haven't yet traced the vehicle I'm sure they have trawled (or are currently trawling) through all the mobile phone data to establish which other phones were operating at that time in the area, and then followed a similar path to Corrie's phone.