The simple answer is no. It’s very rare for a supplier to resort to the lengths of disconnecting a customer’s energy supply.
Disconnection is usually a suppliers’ last resort, when all other avenues have been exhausted in trying to recuperate debt from a customer over a considerable time. Before disconnecting your premises, your supplier must make a reasonable effort to contact you – through several mediums (email, phone and letter).
In addition to an outstanding balance, your supplier has the legal right to disconnect your supply if you have unlawfully altered your premises’ energy meter. An unlawful alteration would be any modification that changes the function of the meter, most commonly to bypass the meter and reduce the amount you’re being charged for energy.
Provided you are not in debt and you have not altered your meter in any unlawful way, then there is very little chance that your supply will be cut off during a switch – even if either supplier chooses to block the switch. In the event that your switch is blocked and your current contract ends, instead of your supply being cut-off, your current supplier will move you onto more expensive out of contract rates until a resolution can be found, and a new contract is organised.