Tim,
You may have solved a 40 year old mystery for me. As a kid I remember my parents taking me on holiday to stay at Whitemead Park and during visits spread over a couple or three years my sister and I discovered an old gutted steam engine on the sidings nearby which provided hours of fascination. I’ve tried a few times to find out what engine it was but to no avail. It now looks likely that your 1977 photo was the engine in question. Thanks !