Vauxhall Astra TwinTop CDTI

Aimed at the likes of the VW Eos and forthcoming Ford Focus CC, the TwinTop mixes style, economy and performance. Sleek and aggressive exterior styling is complemented by a user-friendly and surprisingly spacious interior.

And because Vauxhall's engineers were told how much space the three-piece folding roof was allowed to take up, the rear deck is far shorter than on some rivals, meaning plenty of legroom and a generously sized boot.

Delivering 320Nm of torque - 60Nm more than the largest petrol variant - the 1.9 diesel provides impressive mid-range pace. While the engine has to be revved to get the best performance, you rarely need to drop down from sixth gear when cruising on the motorway.

On more challenging roads, the Astra's steering is nicely weighted, and offers plenty of feedback. With the roof in place, the chassis feels taut, and the TwinTop re-mains largely free of scuttle shake. But on our demanding test route, we noticed a few squeaks from the dashboard.

Generally, though, refinement is good, and wind and road noise are minimal with the top up. Fold it, and buffeting is obviously more of an issue, but even so, the cabin is still a relatively calm place to be - especially once you have slotted in the £150 wind deflector, which we think is an essential option.

Removing the roof from any car tends to have a negative effect on the driving dynamics, and the TwinTop is no exception. There's more chassis movement over rough surfaces, and it doesn't corner nearly as well as the Astra hatch.

Even so, while the Ford and VW prepare to battle it out at the top of the sales charts, we can't help but feel that the Vauxhall may just have the edge. At nearly £1,500 less than the equivalent Eos (and a second quicker over the 0-60mph sprint), the stylish TwinTop looks like the smart choice.