PDA's and palmtops mobile phones? Any reccomendations?

I am looking for a decent handset that will play mp3, have very good internet capabilities, mobile email, telephone, slide out qwerty keyboard, calender for appointments- possibly a camera. Basically i want a palmtop mobile phone of a reasonably small size with good technical features. This would be for personal use and work appointments only. I do not really want to spend more than �200/300 on a handset. Also any ideas what networks would support the phone you recommend and an estimate of monthly costs?