Heart-warming lambs with jackets - and a query about not so nice cat behaviour

Take a look at this - people have been knitting jackets to keep baby lambs warm

And now the difficult part. My neighbours have several cats that poo in my garden [er, the cats not the neighbours]. They don't bury the offending mess but leave deposits on the lawn - not the sort of deposits that increase my bank account. I never feed these cats but do pet them. Very occasionally, if the large black one is soaking wet [they don't have a cat flap] I let it in, and sometimes it sleeps overnight. I like cats generally but not the horrible stuff. Is there any way of preventing this behaviour. I bought a set of cat silhouettes, but saw the black cat cuffing it. I then fixed these to the top of my raspberry trellis to deter birds - but the blackbirds and thrushes use it as a perch.