As can be seen, from studying the list, the majority of the checks, are so easy to carry out, yourself. It looks comprehensive, but is so easy to do.
The gas checks are probably the most difficult, but, remember that LPG, has a built in pungent smell. This is for safety, and makes it quite obvious, if there is a leak.
As a long time motorhomer, I've never had a professional Hab Check carried out, and consider them a waste of money. They didn't even exist, around 20 yrs ago, and, IMO, were just another way to make money.
It always amuses me, when people say that it gives them peace of mind. How do they know if the checks have been carried out correctly, or even at all.
From a practical point of view, during regular use, of your van, you will be carrying out most of these checks, anyway. It will become obvious, if there are any problems.