Thankyou kind sir, all very interesting indeed, and yes I'm very much inclined to agree with you now wrt the names not being connected, ah well,

I can see a place called Blackrock (one word) marked on the old OS maps, which isn't surprising as the British History site states

"North of Lydney town there were a few outlying dwellings, the earliest of them probably the Holms, west of the Bream road. In 1558 it was the centre of a freehold estate belonging to the Hyett family, which sold it to the Winters in 1600, and the farmhouse was rebuilt in the 19th century. There was a farmhouse at Blackrock on the Bream road further north by 1600."

http://www.british-history.ac.uk/vch/glos/vol5/pp46-84

This superb old photo might be the Farm house
https://www.sungreen.co.uk/bream_glos/bream_house.html

atb J.