it depends on how you define "approved". There is no official 'approved' status for block paving contractors, but some of us in the industry are trying to do something about that.

Anyway, assuming you have a 'standard' driveway laid by a reputable contractor using quality products, it can easily take the weight of a family car, a Tranny van or a caravan.

The strength of a driveway really depends on what the existing ground is like, but, assuming you're on anything half decent, a standard 100mm sub-base with a 35-50mm bedding layer and then a 50 or 60mm block should suffice for a caravan hard-standing

If you have any concerns about the existing ground, you could beef up the sub-base to 150mm and use a geo-membrane between the sub-grade and the sub-base layers.