part time ?

[newlifebegins]

thinking to cut to 3 days a week. is it better to request it by email/ letter? do I need to say reasons?

will my part time contract ( permanent) - be as secure as full time?

It may be suitable for you but what about your employer ?
This could backfire on you as you may end up keeping the same workload but less time in which to do it and for less pay.
Or, your employer could issue you with new terms and conditions and let you go in a couple of months and employ someone full time.