I can remember Thomas identifying this next location several years ago, but for some reason when I moved my blog, this one was forgotten about. The location is the one where John Chen's body is dumped after the bungled kidnapping. The big clue here was the building at the back that belonged to the Koon Lam Vegetable Marketing Co-operative Society. It looks as though the Vegetable Marketing Co-operative society was/is part of a larger organisation, the Vegetable Marketing Organisation, that was set up post-war to encourage local farming as a way to help recovery from the occupation.
The Koon Lam branch ( the name on the building reads from right to left : 管欖區蔬菜產銷有限責任合作社 ) was situated in So Kwun Wat, now part of Tuen Mun District, and you can see an old picture of it on the VMO website. But here it is back in the 80's when it was the site for a fictitious murder/body dump.
Unfortunately for me, So Kwun Wat has undergone a significant amount of development since the filming and the whole area has seen not just small house development, but also large residential developments and even a couple of large schools. All this means that finding the exact location of this little building is a bit difficult, but judging from a few visible landmarks I think it is safe to say that it stood on the side of So Kwun Wat Road. If you compare the mountains at the back of the second from last picture, you can see they match with the ones in the Streetview below.
And the hillock behind Gordon Jackson in the bottom picture looks very much as though it is the small hillock that is now hidden behind the Mrs Cheng Yam On Millenium School at the far end of So Kwun Wat Road.
Anyway, perhaps someone out there can be more exact, but for the moment I have marked the location along So Kwun Wat Road behind the Avignon development.