They can go to Court to try to get an order for sale - or, if the suspended order already gives them that power & they try to exercise it, you can apply to Court for the order to be varied.
However, it would seem to be very unlikely that they would do this if they would end up with no money. It is bound to cost them something to get possession & then make a sale, which the mortgage lender could quite possibly frustrate as they would not get a full repayment either.
It is a complicated situation & you could get some advice on it from any free local debt or housing advice agency, or CAB or Shelter.
The least you should do is keep in touch with the lender's solicitor, giving them full details of your present income & expenses so they can see you can no longer afford the £200. CAB or any free debt advice agency could help you prepare a financial statement if necessary. Make sure the solicitor is aware of the value of the house (get it valued by an agent on the pretext that you are thinking of selling, & give them that in writing) & of the outstanding mortgage.