I don't have a good template, but I made sure I included in mine:
- My intention to take leave
- How long I wanted to take leave for/return to work date
- When I was beginning my leave
- How I would like my entitlements to be paid
- A bit of a disclaimer line telling them that if there were any changes due to health concerns that I would give them as much notice as possible

Both my manager and the HR department seemed happy with that. I was also required to give 10 weeks notice of my intention to take leave, but only have to give four weeks notice of my dates.