FLexible working application - how to handle it

[Tumtitum]

I'm currently on maternity leave, due back early next year. I want to go back part-time (was full time before). I work for the NHS and hold a caseload. My manager has responded very quickly to my application stating that it is unlikely they will be able to accommodate my request due to service needs. They have suggested they might be able to cut my hours by one day - which is not what I want.
My plan is to hopefully only go back for a year, and during that year get pregnant again with our second child. I will then leave, as it's not affordable for us to pay for childcare for two pre-schoolers. In my profession I have to work a certain amount of hours in order to renew my registration so for this reason, and obviously financial gain, I plan on starting agency/locum work when DC2 is old enough.
In reality, if I don't get what I'm asking for then I will probably hand in my notice as soon as I am able (I have to return for a few months otherwise they can make me pay back my maternity pay) and either look for a part-time role or start agency/locum work at this point - this wouldn't be my ideal though as when I get pregnant agency work may become harder to find.
I'm not sure how to handle things - should I be brutally honest with my employer and state that I will leave if I don't get enough flexibility, or should I negotiate without letting them know that I will probably leave?? I've always got on very well with my team and have a huge amount of loyalty to them - but my manager is new and I haven't really worked with them before.
Any advice welcome, sorry if it's a bit jumbled!! :)

[Littleladybird14]

I'd put your request in writing if you haven't already, sure the NHS will have a standard application form. Justify as much as you can how it would work for the business - don't discuss why you need this change and how it will benefit you, this is a business case so focus on your workload etc. Provide as much detail and suggestions as possible as to how it could work. They will normally schedule a meeting to discuss your request and consider how it might work. They will need to evidence why they cannot manage your reduced hours and unless they are clear with this you may be able to appeal. Another alternative is to suggest them using a trial period for your reduced hours so they / you can see how it was would work. This may help you secure your request or at least provide you with more time before you have to leave and ensuring you have returned for the time period required for your maternity leave payments. I wouldn't discuss your long term intentions at this stage as not something they need to know and may be less inclined to suppprt your request
Hope this helps!