Housesittersuk seems to be the biggest UK only site and only £29/year so possibly worth a try. There’s also House Sit Match £89 the lowest tier fee and appears very similar to TH but I can only see 26 sits listed (not sure if that’s the extent or only a preview as a non member). Might be worth asking. It covers UK, Europe, US, Canada.
There are others Rover, pawshake, pet sitting angels, Some of these are paid services. I have no experience of any of these.