What kind of car do you have? I'm thinking to buy a Berlingo Multispace with a view to stealth camping in it when I need to go down to my University every other week for a couple of months. You can fold the back seats down and set it up as a mini-camper with a bed in the back. It has quite a following as DIY mini-camper in the UK.
RE: What I Learned from Sleeping in my Car for a Week - It's Not as Bad as You Might Think!