Say you like the idea of a BMW 3 Series but don't like the styling and weight compromises brought about by the metal folding roof. Or a 1 Series Coupe would appeal - if only it looked less awkward. Then BMW's 1 Series Convertible is your car. As long as you can afford the usual high BMW up-front prices, the rest of the story is pretty much all good news. Rear wheel drive means exemplary handling and BMW's EfficientDynamics technology means cheap, green motoring.

It's rather curious that it's taken so long to see a convertible in the 'premium compact hatch' segment. You'll more likely know it as the class that brings you small cars with prestigious badges - models like the Mercedes A-Class, the Volvo C30 and the BMW 1 Series. The danger for all these brands is that a drop-top version of any of these cars would be priced uncomfortably close to their existing larger cabrios.

BMW, being BMW, have gone ahead and produced this 1 Series Convertible anyway, even though it indeed sits just a few thousand pounds below the price of a 3 Series Convertible. Perhaps one reason why is the desire to give buyers a choice between the 3 Series' metal folding hard-top and the 1 Series' lighter, prettier and less stylistically compromised fabric roof.

All 1 Series Convertibles are reasonably rapid, even the entry-level 118i reaching sixty in 9.3s on the way to 130mph. The flagship 135i almost halves this acceleration figure and has to be restrained (why?) at 155mph. Being rear wheel drive, the 1 Series is always going to be the default driver's choice in this segment, though we're not huge fans of the electronic power steering fitted to all variants except the flagship 135i. It operates on an 'on demand' basis, reducing engine output normally needed to power the steering hydraulics.

Buyers choose between either six-speed manual or automatic gearboxes. Steering wheel-mounted paddles enabling manual shifts of the auto 'box are standard on 135i cars and optional on 125i models. 135i customers get BMW's electronic differential lock which electronically slows the spinning inside rear wheel to enhance vehicle traction when the car is accelerating hard out of corners or tight bends. In this situation, it electronically slows the spinning inside rear wheel to enhance vehicle traction and ensure that all available power is transferred to the road.

"No other convertible in the £15,000-£30,000 price bracket will be anything like as good to drive as this one?"

Should you be careless enough to be about to roll your car roof-down, a sensor will register the imminent danger and, alongside the relevant airbag deployment, two roll-over bars will extend from behind the rear seats in a fraction of a second to protect the safety cell.

The 1 Series Coupe was obviously designed with a Convertible model in mind. Both cars share a virtually identical silhouette, with long bonnets, short overhangs and set-back glassy 'greenhouse' proportions. The distinctive, horizontal shoulder line runs from the front of the bonnet, through the long, frameless doors, and onto the end of the boot lid.  From the rear, the boot lid finishes in a discrete lip spoiler that houses the integrated third brake light and typical L-shaped rear light clusters use LED-powered light conductors.

This drop-top model features a fabric roof that opens or closes in 22 seconds, and at speeds of up to 25mph. The roof material is available in classic black, beige or, as a world first, an innovative anthracite silver fleck which is a fabric material interwoven with fine shiny metallic fibres.

Inside, BMW reckons that there's space for four occupants, though the cabin isn't as large as that of, say, convertible Audi A4s or a Saab 9-3s. Still, there's a respectable 305 litres of boot space with the roof up (260 litres with the roof down). A nice touch is a 'convertible' setting for the air conditioning when the roof is down.

Prices start at around £24,000 for the 120i and just over £26,000 for the 125i variant. Though based on the 1 Series Coupe, the Convertible offers a wider range of engines. The two models share 177bhp 120d diesel and 306bhp 135i units, a selection to which the Convertible also adds three more petrol derivatives: a 143bhp 118i entry-level variant, a 170bhp mid-range 120i version and a 218bhp 125i model for those who can't quite stretch to a 135i. Sadly, it does without arguably the best of BMW's 1 Series engines, the twin-turbocharged 204bhp 123d diesel, only currently offered in the Coupe.

In common with Coupé models, purchasers of 135i Convertibles receive the M Sport aerodynamic package as standard. This includes a redesigned, sporting front valance with large air intakes assisting engine breathing and brake cooling.  Re-profiled sill panels and a rear diffuser integrated into the rear bumper aim to add to the car's sportiness. The 135i Convertible also features 17-inch light alloy wheels and six-pot brake callipers on the brakes (two-pot on the rear).

A popular option will be leather upholstery with BMW's clever 'SunReflective Leather Technology' to prevent the seats from over-heating in hot weather. This uses 'cool pigments' during production to reflect infrared rays of sunlight. The result is a reduction in the surface temperature of the seat surfaces by up to 20 degrees Celsius when compared to conventional leather upholstery.

As with all of the premium brands, you have to offset high initial asking prices with low depreciation. Since most cars of this type are bought on leases, this process will be done for you. All 1 Series Convertible models benefit from BMW's EfficientDynamics programme that makes them easily greener and more fuel efficient than their rivals. This effectively works through a combination of clever ideas. Brake Energy Regeneration, for example, which uses intelligent Alternator Control and an Absorbent Glass Matt battery to harness engine power that would normally have been lost during engine over-run or braking. Plus there's an Auto Start-Stop system that cuts the engine in urban traffic when the gear is deselected and the clutch pedal raised.

The result of all this is that this BMW will cost you significantly less to run than, say, an Audi A4 or Saab 9-3 drop-top and not much more than a cabrio based on a cheaper, more mainstream family hatchback - say a Volkswagen Eos or a Ford Focus CC. The only issue for buyers will be whether the 1 Series' interior is large enough. A a comparison, an Eos' boot holds 75 litres more than the BMW's with the roof up (though curiously 55 litres less with the roof down).

BMW's biggest problem with the 1 Series Convertible will be the impact it will make on 3 Series Convertible sales. For us, the 'One' looks to be the better buy, being cheaper to buy and run, better looking and more agile. True, it's slightly smaller - but not much.

The competition from rival models made by other brands with larger cabins and boots is tougher but the BMW still looks appealing, this drop-top the only 1 Series derivative you could actually call pretty. No other convertible in the £15,000-£30,000 price bracket will be anything like as good to drive as this one - or as cheap to run. If you can stomach the upfront investment, this car is a choice that ticks most of the other boxes. And, importantly for a convertible, it makes you feel good about doing it.