This is what I know, to which @Glos-Guy has given the answer!
While some dealers will allow you to place an order prior to the 3 month opening window, this is on their system only and the dealer wil not & cannot put the order onto the Motability system, untill the ist day of the 3 month perios at the earliest.
If you order a car on a Sunday, the dealership will place the order onto the system and the order process will typically be signed off on Monday, however you are technically bound by the quarter you order in, so ordering on 31st May will put you in Q1 prices.
However, I’m not sure what your fully asking, as my mind doesn’t cope to well with riddles now I’m getting older😂