I was dreaming of life in the fast lane, and money, and what it could buy. The sun was warm on my face. And when I opened my eyes, there indeed was a castle in Spain — for real. I was sitting in the passenger seat of a new BMW 6 Series Convertible, which I had been invited to test drive on the beautiful roads of Andalucia.

A fellow journalist was at the wheel while I awaited my turn in the driving seat of the sleek machine. But I could not help reflecting that although I was in Spain, I was also, financially speaking at least, in Porsche country — because this car, at more than £70,000, is in direct competition with Porsche . . . .and Maserati and Jaguar, come to that.

But it seems that despite hard economic times for some, the rich are always with us — and BMW management have done their sums.

At the launch presentation managing director of BMW UK, Tim Abbott, said he expected a big demand in Britain — now the second largest market for convertibles in Europe, after Germany.

You can choose between two engines, a three litre turbo, the 640i, and the massively powerful 4.4-litre twin-turbocharged V8 called the 650i — both driven through an eight-speed automatic gearbox.

I drove both and, not being power crazy, would probably go for the 640i: it’s cheaper to buy, more economical to run, and not much slower, either. All you lack with the tamer model is that extraordinary surge of power when you first put your foot down; that feeling you will always be the leader of the pack.

But then again, if you are thinking of spending more than £70,000 on a car and you quibble about a few thousand pounds here and there, you probably can’t afford it anyway.

BMW is marketing the new 6 Series Convertible, and the upcoming Coupe, under the slogan of “joy”; and they’re right. The cars are a joy to behold.

But after watching a fellow journalist parting with a 50 Euro fine at the roadside for speeding, I did begin to wonder whether we are all going mad to hanker after toys like these.

Hanker we do, though, and BMW asserted that, environmentally speaking, “you can have your cake and eat it too” by buying one of these cars — because they knock the socks off competitors when it comes to CO2 and particulates production.

Apparently, these cars are more environmentally friendly than my old workhorse of a 3 Series (which has more than 100,000 miles on the clock) — and I must admit that even I, cynical as I am, began to realise why people will buy cars like this, if they can afford it.

For a start there is the new improved cabin, all luxurious, welcoming Dakota leather. Sink into one of those seats and you feel yourself in control of the world around you, with all creature comforts adjustable at the touch of a button: air conditioning, stereo and of course the 10.2 inch screen, capable of telling you far more than just how to get to wherever you want to go, and easy enough for even a techno-phobe like me to operate.

BMW says the car is aimed at successful business people, such as chief executives, who want to keep in touch at all times. You can check e-mails arriving on your Blackberry via the iDrive system. And for a mere £980 extra, you can have your speed and sat nav directions displayed with Head-Up Display — information projected onto the windscreen.

It seems to me that as time goes on, despite talk of downsizing for economic or environmental reasons, many cars now made by BMW are getting longer and wider, and the new 6 Series is another case in point. It is longer and wider than the outgoing 6 Series Convertible.

Altogether the 650i I drove had about £10,000 worth of extras on board, including ivory white seats (£1,150), and Adaptive Drive (£3,500) to adapt the suspension to the terrain.

Certainly the seats are some of the most comfortable I have ever sat in — apart from my dentist’s — and in the front there is ample leg room even for someone, like me, not in his first flush of youth and 6ft 3in.

And despite the car being lower on the ground than its predecessor there is enough headroom too.

Both the cars I drove also had electric lumbar support (£300 extra). They also contain technology to stop the leather getting too hot should you leave the hood down in the sun.

The back seats remain tiny and are really only suitable for children even for short journeys. Which makes you wonder who exactly will buy the car — though I am sure lots of people will.

To compensate for the small back seats, the boot is reasonably large — even though, of course, the hood automatically folds away into it. Indeed almost everything in this seductive car is automatic.

But back to building castles in Spain. Would I buy a BMW 6 Series Convertible?

Well, yes. And my old 3 Series does need replacing . . . Then again, I had better get real.