Best time for dealership offers/deals

[Romp]

When is the best time for dealership deals and offers? Appreciate end of quarter,end of tax year etc but are there any other standard offer periods ? Say just before a model upgrade comes out etc? December ? Etc etc z. I don’t know actual facts .
I’m due a change in the coming months as pcp ends and trying to time things right at either a bmw, Audi or jaguar dealership but would like some experienced advice on this from those ‘who actual know as fact’ so I get myself the best possible deal
Cheers