It is likely you will need prior approval to installing a ground source heat pump from the regional District Network Operator (DNO) who manage the electrical infrastructure. They will need to ensure that the mains connection to the subject property and that their own cabling/sub-stations have the necessary capacity to meet the potential demand. With the advent if inverter driven heat pumps in recent years this is not as big an issue as it once was however for larger output ground source heat pumps it may be necessary to upgrade electricity supplies.