I have the KoJack and it is OK. A little on the heavy side, but does the job very well. It also comes with a case. This is the bigger of the two models that they make in this range.
I agree with David, buy a KoJack. I have one and they are pretty great, also it comes with jacking points that 1. screw to the chasis and 2. act as a levelling aid when you arrive on a site.
I have the Kojack original scissor type and its very easy to use but the spirit levels are not easy to use without lying on the ground
It sounds good on the advert but its much easier to use a spirt level on the van floor standing up!
I have the Nissan X Trail (new model) and after removing the polystyrene and the original car jack the Kojack fits into the jack space in the car boot and fits the car jacking points as well
Thus excess weight is trimmed as only one jack is needed for car and van
The Kojack uses the same mounting holes as the Alko jack and if the van is older and is pre the 2 Alko holes then it would be a simple matter to drill the chassis and no warranty issues should arise due to the age
A bottle jack would be less stable than a small trolley jack and Lidl had some very good cheap ones for under