I have that Lazy Afternoon album on vinyl. Paul Downes is listed as the producer on that and several of the songs also appear on his early solo albums.

I'm Looking Out For Number One and Sit You Down are certainly Steve Knightley songs. The best version of Sit You Down is the one from the DVD of the Show of Hands RAH show in 2001, where Paul Downes joined them on stage. I don't think Steve has ever Officially issued I'm Looking Out For Number One himself.