I think with these things Paul from experience it’s probably best to go to a local detailer if you require extra protection (paint correction / ceramic coatings) etc. Than the dealer direct.
I have a friend who is a detailer in the north west and the amount of work he gets from people who have had new cars prepared by ‘dealers’ is crazy. Looks like some of them clean them with a Brillo pad.
May be worth checking locally to you to see if someone who does this kind of work day in day out and takes their time can come up with a reasonable price.