The Single Market prevented countries from imposing tariffs on imports/exports within it's borders. So if you are a UK farmer, and you want to sell your grain to France, France cannot impose a tariff on it that is any different to any other country in the SM. (The history of the SM is steel and coal).
So out of the SM, France is allowed to impose whatever tariff it likes on UK grain. If that makes UK grain more expensive than grain from an EU country, then c'est la vie.
The opposite is also true. Now a French company could charge a UK company more for it's widgets that it charges a German company. If those widgets are used to build cars, and UK cars become more expensive than German cars then ... c'est la vie.
Of course the UK can offset higher component prices by reducing wages.
(One notion did occur to me, and that is the fact that out of the Single Market, there is no reason why car manufacturers can't charge more for RHD cars. Which leads to the amusing prospect of UKIPpers clamouring for the UK to adopt left-driving to have cheaper cars
)
Of course, nothing is that simple, and a lot of horse trading will be needed. However I can guarantee one simple fact. Whatever, however, and whenever these negotiations take place, the ultimate loser will be the end consumer. Look how every shift in exchange rates or oil prices is pretext for a price rise. Still that is what 52% wanted, so as long as they are happy.
Currently we're in the quiet before the storm bit. Just wait till holidays start going up 10, 20% (that weak pound) ...