The specific distro is called MX linux and is based on Debian stable.
https://mxlinux.org/
I've tried more recent kernels 4.7 and firmware from the Debian testing repositories.
Also tried compiling from source on github.
No joy ... some wireless networks are fine (very fast) and others are unusable.
The wireless networks which don't work on my new HP Laptop work fine on my old 32-bit netbook running the same OS.
Dual boot system Windows 10 works ok, but it's Windows.
This is definitely seems to be a hardware / driver problem.