You have my sympathy. Our front garden is open plan and owners let dogs cock their legs on our trees in broad daylight!
To add to the list of possible wildlife culprits - it's amazing how much a big hedgehog can produce and they do favour a nice garden lawn. When you've nothing better to do you can find pics on google to help identify different animal poos (sorry, hope you're not having breakfast).
The main room in your house...


