Before it became a Wallace-and-Gromit ghetto, model animation was pioneered by Cosgrove Hall - and this is arguably their magnum opus. Beautifully produced, lovingly detailed, with a great vocal cast and classy score, it has the nerve to stick closely to the book. As a result it is the best screen version by miles and, in my opinion, likely to remain so.
Some kids may find it a bit slow by today's standards; but if they stick with it, they may just discover that not everything has to be frenetic to be enjoyable. If not, what the heck - like the book, it's probably as good (if not better) for grown-ups.