David.
No one is disputing the fact that your dealer has placed an order on his system for the 40 and that it will be delivered as a 45. This is because the 45 is slightly cheaper at retail than the 40 and given it is an upgrade every customer would want to receive the 45.
No one contests this fact.
What people are concerned over is the imponderable that Motability will allow you to receive the 45 in place of the 40.
As ‘great’ as your dealer is – he does not have the answer to this. It may be the case that the 45 appears on the Scheme next week with a larger AP than the 40, in this instance they may choose to cancel all outstanding builds for the 40. They can do this as they are paying for the car.
I do hope this goes some way to help you understand why people on this forum are concerned.