As outlined above Carol, brexit makes a huge difference to the future of the Sunderland plant, the decision on where to base future production lines will be massively influenced by this. If we don't have tariff free access Nissan in Sunderland will cut production.
In my answer to your previous question, the main factors influencing demand for BMW, Mercedes, Audi and a lot of Volkswagen branded cars are not price.
The Beamer, Merc and Audi brands are particularly safe because there is only one British company that could be seen to be a substitute and that is Jaguar, but there are further determinants for the demand. Quality, the brand image, after market servicing, re sale value all come in to this decusion and are more dominant than price and here's why.
Someone wanting to spend 30 -100k on a car ( where these cars are generally priced) is not going to be put off from one car to another by a 10% difference in price, for example if you think the BMW 5 series ( between 31 and 51,00 depending on specification) is the best one, you aren't going to lump for another car because its slightly cheaper. Essentially if you think the beamer at £34,100 is a better car than the equivalent Jag at £31,000 you're still going to have the beamer.
At the lower end, UK built cars would be more competitive in the market where price is a major factor, but I don't think it will make it quite as competitive as is being made out here.
Lets take again the Nissan Pulsar, which is a reasonably priced family hatch back, now it has to compete already has to compete against a large number of cars in the market which are cheaper, so the tariff may make it more competitive with them. But again other the factors come into play here, a price difference between the British made Nissan/Toyota/Honda/Vauxhal of between of between £1,000 and £2,000 and another brand may not be enough to change the customer's decision from another brand.
Also on top of this, the full effect of a 10% price difference may not actually be felt because a number of the components for all of these cars are imported from factories in the EU and of course will be subject to tariffs too! On top of rising energy and raw material costs, the full 10% impact may not be felt and therefore the British built cars will not be as competitive in the UK market as we would hope them to be. Essentially if the price difference is 7-8% rather than 10% price probably won't make that much of a difference at this level either.
The issue is further exacerbated by the fact that Nissan Sunderland exports about 70% of its products to the EU, these cars would be less competitive with the European made cars with their tariff, but also will have the slightly increased costs of production to add on too. With a larger range of choice of vehicles that do not have the tariff on them, would Nissan remain as competitive in the EU as it would need to be for Sunderland to continue being its main plant?
240,000 of the cars produced at Sunderland last year were Qashqui, ore than half of its output. With the new range aiming to start production in 2020, Sunderland is unlikely to get the investment that will replace this production line as planning and investment would have to start in the near future.
Combine all of the above with Nissan having plants in Spain and has the alliance with Renault, I don't see a rosy future for Sunderland.
Now thankfully our luxury car market will not be effected, no buys a Porsche over an Aston because the price has changed by 10%, and certainly not a Bentley or Roller.