Snap! Great find. I have one of those too. If I remember correctly side 1 had BBC 'Noel Edmunds' giving instructions for assembling a train set, but wait for it . . . side 2 has an 'Authentic Railway Sounds' track for playing background noises on a layout (e.g. trains, loco whistles and horns, station noises, track clink, passing trains, and station bustle noises, etc).
When I found it a few years ago it gave me the idea to digitise it and build an iPhone app for playing various layout sounds using other recordings I have (e.g. distant trains, passing trains, station noises, background ambient noises, traffic, etc).