Sales of MPV vehicles are booming, largely because they're regarded as more versatile than normal saloons or estates. But in one major area - probably the major area - they're a con.

MPVs, such as Espaces and Galaxys and Sharans, offer seven seats, most of which can fold and swivel and tilt and slide, and change from lounge chair to picnic table at the merest pull of a lever. But key to their claim to versatility is that the seats can be removed completely - by that measure, they're about as practical as a backpack made of lead.

Sure, if you've got strong enough hands, bad enough finger nails, and tough enough skin, you can just about perform the exertions and finger gymnastics required to remove the chairs. But to us mere mortals, it's far too much aggro. Most MPV owners I know stick to the seven- or five- seat format, and rarely change. In practice, the seating format is as rigid as a nun's vow.

Not only are the chairs of all MPVs - from the baby Mercedes A-class to the class-topping new Renault Espace - awkward to remove and replace, but what on earth do you do with them when they're out? Even if you own a garage, do you really want to put your posh velour-covered chairs in the corner, to gather dust?

And for us urban dwellers, who find it hard to liberate enough house space for our books let alone leftover car seats, the problem is even more acute. I suggested putting the rear-most chairs of a recent test Espace in our lounge, but Her Indoors insisted that the purple velour clashed with the cream Heal's three-piece suite. And she found the metal "legs" of the Espace seats unsightly.

Even if you manage to extract all the back seats from an Espace in order to carry that chest of drawers to grandpa's, what happens if grandpa and grandma want to come home with you? The answer - sorry but I left the seats at home - seems rather pathetic.

It's partly for the above reasons, and partly because my wife still can't come to terms with driving a glorified van, that we recently decided to buy a three-year-old Mercedes estate, to cart around our three young boys and the odds and ends (travel cot, pushchair, footballs, Power Rangers, Street Sharks, sweets, Lego, toy cars, books, comics, rucksacks etc) that invariably accompany them.

What particularly attracted us was the optional rear-facing bench, which boosts the people-carrying capacity to seven. The two rearmost chairs fold up or down with great ease. If you wish to turn your estate from a cupboard carrier into a people carrier, it's a simple matter of folding rather than removing/replacing - assuming, of course, that the MPV seats are nearby.

Fortunately, there's a new people carrier that doesn't require its owners to skin their knuckles every time they want to alter the seating arrangement, and doesn't require unfortunate grandparents to lie low in the rear. It's the new Vauxhall Zafira, and it's still a year away from the showroom. Vauxhall reckoned, quite sensibly, that it's far preferable to leave seats in than to take them away, so the back five seats of the new Zafira all fold.

The rear two seats fold flat into the floor, allowing the middle bench (which can seat three) to slide over them, if necessary. And the middle bench folds forward, out of the way, in the good ol' estate style. "It's just so much easier than the normal MPV arrangement," Vauxhall/Opel's head of engineering, Peter Hanenberger, told me at the recent Frankfurt Show, where the Zafira was unveiled. (Quite where this puts the recently launched, and orthodox-cabined, Vauxhall Sintra MPV, I didn't dare enquire.)

The Zafira is a small MPV - it's of Renault Scenic rather than Renault Espace exterior size - and it strikes me as being potentially the biggest leap forward in MPVs since the original Espace, 13 years ago. Why buy a similarly sized Astra or Golf, when the same sort of money will buy you a car with seven seats and genuine versatility? Or, for that matter (and this is a little harder for me to come to terms with), why buy a Mercedes estate?