@Susannah, the answer to your problem lies in the question … attracting more sitters requires the listing to be more attractive to sitters.
In our personal opinion, as experienced sitters, your primary photo is an immediate turnoff. Lots clutter. Photo of kitchen shows pots & pans drying and what looks like arts and crafts. Encourage tidy up, put away excess stuff and take new photos.
Christmas is an exceptionally competitive time of year. Many Pet Parents travel. Many housesitters stay home with family (or charge for their services). Recent THS Forum thread noted 5,000 unfilled Christmas sits, including 1000+ in UK. Very competitive.