"The present tenants arrived home to find their home forcibly entered, a warrant lying on the stair and their meter removed and a prepayment meter installed. If you don't find that most disturbing, well frankly - you should!"
I find the whole episode disturbing and I believe that somebody told porkies to the JP who signed the warrant. Leaving aside the fact that the previous occupant left "properly", with meter readings taken, etc., effectively a warrant was obtained to enter the premises when they were occupied by somebody other than the debtor. The debt accrues to the occupier who took out the contract, not to whoever happens to be occupying the premises currently.
When requesting a warrant the suppliers are obliged to tell the JP what the current status of the premises is (i.e. unoccupied, occupied by the debtor, occupied by somebody else, unknown, etc.). As I said earlier, I do not imagine a Justice would issue a warrant to force entry to premises occupied by somebody who is not the debtor. There is no justification for it.