They were forced to abandon a Freeview slot when another broadcaster (Discovery Networks?) outbid them for the same slot when the contract came up for renewal. (It was actually the slot used for Bid TV but Sit-up kept Bid on Freeview, dropping Price-drop instead.)
However more Freeview slots became available elsewhere when transmission equipment was upgraded, and I think Sit-up made a private deal with the owners of a particular channel group (multiplex) to let them have a slot (as opposed to having the slot auctioned off), which enabled Price-drop to return to Freeview.
I suppose that dropping an existing Freeview slot might be an option depending on the terms of the contract, but having both channels means that they can flog two bits of tat simultaneously as opposed to one even if they're paying to broadcast two channels. Other money-saving options might be to introduce more prerecorded auctions for Price-drop or to reduce its broadcasting hours.