Don't hate me - genuine Brexit related purchase question

[anotherv60]

I was chatting today with my friend who works for a management consultancy company; he has seen a breakdown of expected cost increases for vehicles sold in the UK if we have a no deal brexit and its forecasting Volvo final sale prices will jump between 14.6% and 18.4%, I was surprised as I was under the impression that the WTO was 10% on cars, but he pointed out if companies allow for a 1% margin reduction then for a manufacture such as Volvo who uses GKN products for its vehicles (made in the UK), it will be paying import levies on the components as well as the sale of the final car, hence it will be higher than 10% tariff….

The question I have for anyone in the know is if you sign a deal to purchase or lease a car now for a fixed price, does that price have to be honoured if the vehicle is delivered post brexit? The higher figure (18.4%) is for 4WD vehicles (including T8) and it basically wipes out the discount that is currently available now, I’ve priced up some V90CCs and this impact is an extra £8464, on the spec I’d like so not small change!