When we moved into this house it was with Scottish Power and they tried to insist I either had to pay the £100 up front or set up a £100 a month direct debit.
Since I intended to switch suppliers immediately I had no intention of doing either, I explained that I was happy to pay for the electricity, but not to pay up front and then try and claw it back. Wasn’t good enough apparently, in the end I just refused to supply any details, and swapped to Eon who I gave my initial readings to so never heard from SP again.