cant speak for the other countries mentioned but BMW's UK production is very limited indeed - small petrol engines (MINI only?) and some metalwork, they only assemble MINIs here. so the prices in the UK would rise by very nearly the revaluation of the currency.
then theres the rest of europe, whose currencies would mostly be devalued relative to the euro and would therefore be looking at more than 50-100% price rises. BMW would have to drop prices and slash margins to almost nothing to survive this, although lower costs for imported raw materials would offset it slightly. this on top of squeezed demand due to other fallout from the eurozone breaking up (no credit, higher unemployment etc etc.)
in this truly global economy events like this have knockon effects which are sometimes hard to foresee. aston martin are 50miles from me, their engines are built in cologne so their prices would go up a fair bit. on the one hand they would probably steal some sales from Merc and Porsche, on the other hand they would lose sales to ferrari ...