One approach to this, depending on the energy company, and subject to checking the precise details of how it will work, e.g. what will happen if you change suppliers before you've paid it back, would be to consider paying extra to your fuel company so that your account is in credit.
I do that anyway in the warmer months. But then I'm a weirdo that keeps some extra money on a credit card account, i.e. treating a credit card like a pre-pay card. I do that having previously found myself in hospital and at a loss how to pay bills and not wanting to get in debt. When, in the past, a sudden crisis (fraud/theft not covered by insurance) meant racking up a credit bill fast, I took stuff to a pawnbroker rather than owe on a credit card.
Ironically, I felt ok in the past about having a mortgage, but that's a bit like pawning something anyway, because the lender has a charge over the property.
Another thing to do that wouldn't be not-owing but would have a similar personal & psychological effect if you can do it would be to put £200 aside in a savings account or 'under the bed' or to label for yourself, if you have them, £200-worth of pawn-able/sellable possessions.