Must be lots of mining areas similar to Gateshead with flooded coal mines: https://www.bbc.com/news/science-environment-60772187?utm_source=pocket-newtab-global-en-GB
It's a great idea. A lad I worked with at Jaguar spent most of his redundancy money on a ground effect heating system and solar panels (luckily he has half an acre of land). His energy bills are effectively zero now (even more luck).
Wanted a heat pump when we restored our house and with a large garden an expensive bore hole would have been un-neccessary as we could have had a coil running around the perimeter and also round the fossa recovering heat from waste hot water but it would have needed a far bigger supply to run it. (Like a fridge when the compressor kicks in it initially pulls a lot of current) Standard here is only 3kw in rural and we have 6kw You can go up to 12kw but you pay by the kilowatt supply level in standard charges which adds up) When they did the calculations it was borderline feasible for our property and, very expensive. We are only now just going down the solar route.
