IamIan,
Take a gander on this discussion group. Geothermal forum. Probably half a dozen build threads where members have rolled their own. My favorites are Randy and Jake (randen, memphis). Randy used a smallish window AC unit, Jake built a DX ground loop from scratch. Jake amped his up by adding an indoor dehumidifier loop. Both run off 120 volts and save energy.
https://ecorenovator.org/forum/showthread.php?t=4413
https://ecorenovator.org/forum/showthread.php?t=3247