Hi Charles,
I bought a jsbhublock approx one year ago. I am quite impressed with it as a security measure, a heavy duty piece of kit.
It's been discussed on here a couple of times before with one or two members reckoning it would be easy to remove. Prior to buying the lock I phoned up the manufacturer to ask a few questions. He is a caravanner himself as well as being an engineer and had the misfortune to have his caravan stolen. When he discovered there was not a security device on the market resistant to burning he set about designing one. All those who have said they could remove it in minutes have been invited to demonstrate to him how they would do this.. none have.
The only downside to it is that you have to jack up your caravan and remove the wheel to fit the hublock, perhaps a bit too inconvenient for some. I only use mine when the van is in storage, at other times I use the alko wheel lock. I find I can fit the hublock in approx 15 to 20 minutes. It gives additional piece of mind and I would recommend it.
I would also recommend you phone the manufacturer if you have any questions regarding the device. Unfortunately I can't remember his name but he is very friendly and helpful. I would also recommend buying the optional wheel guides ( perhaps not the correct name), two threaded spindles which help you get the wheel aligned up when refitting.
Robert