Leeds or London?

My wife and I are going to the UK for 6 months between Apr and Oct to live and work. Where's better for us, Leeds, London or some other place? Preferably we want a place where we can both find jobs and cheapish accomm and where the climate isn't too extreme (we're from Sydney, Australia). We'd prefer a mid-size place rather than a big metropolis, but other than that we really don't care where we end up. It's just gonna be like a fun, discovery thing for us as we've hardly travelled outside Australia.