Hi, if he is not enrolled at a state school, then you don't need to deregister him, or ask for consent to home educate. If you've already deferred, then he won't be on the school roll for August, so you don't have to do anything.
I don't know if they will write to you to offer you a school place for the following year, or if you're expected to apply for them yourself - if they do write to offer you a place, you'll have to turn it down at that stage, but you still won't need to ask consent to HE, because he has never actually been enrolled at the school or attended it.
link here to the guidelines The relevant bit is :
"Under Section 35 of the Education (Scotland) Act 1980, parents of a child who has been attending a public school [ie state school] must seek the local authority's consent before withdrawing their child from that school, and the authority must not unreasonably withhold consent. It should be noted that while consent is needed for withdrawal from school, consent is not needed to home educate in itself.
Consent is not needed in the following situations:
The child has never attended a public school....."
Even though the nursery is attached to the school, it is not itself a state school, so doesn't matter here.
HTH!