Use the long-established and reliable https://www.booking.com as a resource (you can book through it as well, obv). It lists pretty much all accomm within the EU and a huge amount in other continents/countries too. You'll find hotels, b&bs, guesthouses, self-catering accomm, hostels.... Only you know what route you're taking from London to Valencia. 1. Put the name of where you plan to stay each night into booking.com. If you want rates and/or to book through the site (I have done so for almost 20 years with no issues whatsoever) put in the date/number of people too. 2. When you get the results look in the menu on the left-hand side of the page and tick 'Pets allowed'. The page will refresh to show only properties which allow pets. 3. Top right of the page is a 'Show Map' button. Click that and you'll see all listed properties in your chosen location and nearby accurately mapped. Use the +/- signs to expand and reduce the area the map covers.