@ayeletfleming first
DON’T PANIC ( easier said than done I know )
Where you are currently located , Is your next sit on 20th also In Amsterdam? There are lots of sits with dogs not cats for those dates in U.K. so a return flight / train / coach ticket to U.K. for ( England, Scotland & Wales ) a sit will likely save you money compared to 10 days at a hotel or Airbnb plus some enriching experiences…
Sometimes these last minute changes can work out to be great experiences .
For example I see there is a sit listed in Edinburgh so you could follow in @Maggie8K ‘s footsteps and visit that city https://forum.trustedhousesitters.com/t/recommendations-for-glasgow-and-edinburgh
Please let us know how you get on .
@Jenny 
when this happens ( last minute sit cancellation) it would be great to have a section of the forum for a sitter to post their last minute availability- just like the section where homeowners can post their last minute sits .
FWIW @ayeletfleming the sit cancellation guarantee would not have covered you if the Homeowner had already told you about the cancellation when you upgraded to Premium . Even if you had been covered , you would have to pay for the accommodation upfront and then claim it back which can take 2-7 months .