A base P85 costs £68,700 in britain, after a £5,000 incentive. That means that before incentive it costs $123,300, including 20% VAT. Without VAT it is then $102,750.
In other words, it isn't cheaper in the UK. Europe seems to have approximately identical prices in all markets, now.
- - - Updated - - -
Germany has significantly more expensive electricity. They've been shutting down nuclear power plants and that has really put pressure on prices.
With electricity costs at an average €0.2965/kWh (in December) and an average of 0.25 kWh/km, that works out to €0.074/km. An M5 uses about 10 liters/100 km, and gasoline currently costs €1.495/liter, so that works out to €0.15/km. That means an M5 costs around twice as much in fuel.