I don't think br*xit is a factor yet but it probably will be sooner or later.
VW UK would of course like to know what tariffs there will be now so as to adjust their prices because with a 6 month lead there will be a large amount of in flight orders with contracted prices that they won't be able to change when at the last minute tariffs get introduced. Those tariffs will be coming off their profits for the in flight orders.
The issue is currently compounded by the delays and a much greater number of ordered vehicles because of it.
Equally though, I'd guess orders will be down overall, because of br*xit uncertainty with consumers and business.