A few years ago, an edition of 'Chaloner' - the Leighton Buzzard Railway's magazine - had an article about the Bedfordshire Brickworks railway system, including some excellent photos.
Very annoyingly, I have just been (very quickly) through my back issues and can't find the exact magazine. I am sure if you contact the LBR at Page Park station, they will be able to get you a copy. I know they keep a small stock of back issues at the station.
HTH.