If anyone else is interested in the #Datatrak LF navigation network, it turns out Alwyn Williams' PhD thesis is on the University of Bangor's website for download:
https://research.bangor.ac.uk/en/studentTheses/prediction-of-the-coverage-and-performance-of-the-datatrak-low-fr/

This contains a mountain of information on the network and how it was set up. It's a long read though - 300 pages.