The optional wind deflector can now be stored behind the seats when not in use, and a new Air Collar system blows warm air around the necks of front seat occupants for open-air driving on cooler days.
The convertible, which sits alongside the 4 Series Coupe, carries a £5000 premium over its fixed-roof sibling.
At launch, customers will be able to choose from two petrol engines — a four-cylinder 428i with 241bhp and a straight six 435i with 302bhp — and one diesel, the 180bhp 420d, which BMW says will be capable of 55mpg. There will also be a choice of five trims, SE, Sport, Luxury, Modern and M Sport.
The entry-level will be the 420d SE, at £36,675, with the cheapest petrol at launch being the 4281 SE at £39,515. The cheapest 435i Luxury will carry a price tag of £44,970.