Paul, we looked very deeply into doing exactly this recently. Instead of selling my house we were keen to rent it out. Needless to say, after talking at length to an agent in Waterlooville, we decided there were too many expenses/pitfalls and we'd be better off using the equity from my house to reduce the mortgage considerably in our new house (when we get one!).
Funny thing is, we're now temporarily renting from that same agent!
Happy to discuss mate.
Paul.