Faced with the prospect of driving the Polo GTI for nearly 1000 miles in two days, I immediately reverted to what John Stevens calls the "prudent Scotsman" side of my personality and decided that fuel economy was - at least temporarily - going to be more important than performance.I wasn't looking forward to it. This is a 178bhp hot hatch which goes like the devil but does not, at first sight, give the impression of being a decent motorway cruiser. As well as using a lot of fuel, it would probably try to separate my vertebrae. I might end up needing an osteopath without having the means to pay for the treatment.I stand before you now a changed man. I was wrong on both counts. Firstly, while the GTI's ride is undoubtedly firm, it didn't cause me any problems; in fact I'd go so far as to say this car is more comfortable on a long journey than several others which are marketed as being "luxury" or "premium" or such like.Secondly, I was as surprised as I dare say you would have been that the GTI's trip computer told me I had averaged 49mpg on the first day and 45mpg on the next. That seemed unlikely, especially since I've experienced optimistic readings from Volkswagen in the past, so I checked how much petrol had gone in at each refill and what mileage had been covered.And what do you know, it turned out that the second reading was actually pessimistic. (I don't know why, but it may be that the mpg you record early on influences the figure you're given later.) My average for the whole trip was 49.6mpg. I hadn't predicted what it would be before I started, but if you'd asked me I might have told you I would have been satisfied with 10mpg less.I've gone on about at this about some length because it reveals something perhaps unexpected about the GTI (and presumably also about the technically very similar SEAT Ibiza Cupra and Skoda Fabia vRS). I realise that you may be more interested in the hot hatch aspect, though, and to some extent that was covered in our recent short test.Having put the GTI to more strenuous work on fabulous country roads (after my mileage marathon was out of the way) I can confirm that the GTI is a splendid little performance car. The forced-induction 1.4-litre engine feels like it must be twice its actual capacity, with its ability to pull hard from almost no revs at all to around 7000, and the seven-speed DSG twin-clutch semi-automatic gearbox is - apart from the usual hesitancy during slow starts - absolutely ideal for road use, even though it wouldn't be my first choice on a race circuit.The roadholding is better still. Corners which require a lot of concentration in most other cars are easy to negotiate in this one, which to my mind combines greater fun and higher levels of safety. The balance is as near perfect as makes no difference - there's no sign whatever of either the front or rear end wanting to break way, or at least not at any speed I'm prepared to contemplate on the public road.The Polo GTI proved to be a fine car in a much wider variety of driving conditions than I was expecting. Nothing in this test, however, altered my opinion that its biggest problem is the existence of those other VW Group models, the Ibiza Cupra and Fabia vRS. The Polo is considerably the most expensive of the three, and I don't think this is sufficiently justified; to me, its greatest advantage is that it has the best steering feel of the three, and I'd grumble about having to pay hundreds or even thousands of pounds extra just for that. Engine 1390 cc, 4 cylinders Power 178bhp Transmission 7-speed semi-auto Fuel/CO2 47.9 mpg / 139 g/km Acceleration 0-62mph: 6.9 seconds Top speed 142mph Price £18,795 Details correct at publication date