Well, you see (practically) all medically necessary costs are covered.
In the case of birth it's proven that in a low risk pregnancy it's safer for both mother and child to have a home birth. Honestly it is. Where there is a medical reason for hospital birth the costs are covered.
Choosing a hospital birth where not medically necessary is a different kettle of fish. In the same way, you'd be covered for breast reconstruction but not for a cosmetic boob job. That could be something one might really want but isn't medically necessary or the optimum thing to do for ones health. Your insurer will be able to explain exactly what they cover, it does vary from insurer to insurer and package to package.
The thing is, if you book for a home birth and then have the MW transfer you to hospital then AFAIK, you have a medical indication and are covered by insurance. 'Discovering' during the early stages of labour that you want / need, for example, stronger pain relief than is available at home is a medical indication of requiring a hospital birth. Basically, it's a formality.
It's something you'll need to discuss with you MW, but as a general rule it's a loophole they're happy to exploit in the best interests of their patients. It wouldn't mean going in any later than you would in the UK anyway and you already said that you're really close to the hospital.
Depending on your income you might be entitled to Zorgtoeslag from the belastingdienst. But that's a general thing, not specifically birth related. A lot of people don't know about it.
I'm intrigued as to where you are, I used to live in Brabant and found them just as over keen to speak English as here. Most annoying indeed, I just used to steamroller through with my (then) awful Dutch 
.
Engels meisje / Engelse meisjes, I think 
. You must be expecting a girl!!