@ iand: how'd it go in the end with the window precautions?
@ folks who think 'house cats' is a bad thing: my cat is a house cat. He was not always so. He used to go out quite a bit. Then one day he didn't come back. He was missing for 6 months and when I found him again (miracle) at the end of our street, he was thin and scraggly and had had something that punctured his left eye, causing it to be all sunken in. His remaining eye had quite a bad scratch on the lens. After 2 weeks being fed lots and given antibiotics, we took him to the vets and had his damaged eye removed.
He mooches in the back yard under supervision, but he is not allowed out on his own anymore. For a start he had no depth perception any longer which sometimes causes him difficulty with familiar obstacles indoors, never mind traffic, other cats and the like.
Is not all cut and dried. Cats may well be independent but 'letting nature take its course' and looking after your animals do not always see eye to eye.