We bought a universal shaped boot liner, waterproof nylon mix of some sort which covers all the sides, cable tied it at convenient points to keep it in place, then chucked an old floor rug in on top so the dogs have warmth comfort and grip.

It gets wet when they've been swimming, when haven't they, and you get muddy splashes up the glass and interior trim which turns to dust when it dries, but it has protected what it needed to.

Might be worth a waterproof seat cover over the back seat of the dog can touch it.

Best solution, cancel the new car, buy an old estate car or preferably a pick up, sorted..:-)

Get a dog muzzle to prevent canine saliva everywhere enduing car with "eau de canine" for ever.

Thanks to one and all for the help ...