Woke up with this bug on my ceiling in my flat (North London, UK) It's about 1inch long and has a distinct upwards curving tail and looks a bit like a green leaf. I think it has orange eyes as well. I assume it's a flying insect but am not sure and haven't bothered it to see how it moves.Have looked at all the ID pages I can find for the UK but haven't found anything like it.
It honestly looks to me like a katydid, of family Tettigoniidae. Another North American grasshopper or, in other minds, it belongs to the locust family. They eat leaves, and the like and a few species of them will eat other insects.