WHBM.. Not wishing to question you, but I would be astounded if that was true. Firstly, I'm not aware of any BM mail flights arriving at 00.30 - well outside the night curfew. Secondly, noise abatement rules, which have been in force for considerably longer than 10-15 years, required aircraft landing at that time to be established in the ILS no closer than 10miles out. Tight-in visual approaches in the middle of the night didn't happen...
There was certainly a very late BM flight from Edinburgh, but this landed around 11pm. I was told that this was often empty but used simply to keep a BM slot occupied...
If someone proves I'm talking tosh I'll withdraw gracefully!