You'll be breaking bye laws if you park on the public highway, and be trespassing if you park on car parks.
You will have to sit inside your van with the curtains closed in case people see you, think about how you are going to get rid of your waste, including toilet waste, where you will get water from and how you are going to generate enough electricity to power your electricals. A tv aerial on the roof will be a dead give away.
You will also have to consider your cooking smells.
How will you deal with your post? Have you got an address to give to the insurance company, DVLA, GP and so on?