Sorry - I keep wandering off!
General things to bear in mind, as I am unclear as to whether this is a campervan or a motorhome.
1. Weight. Many people are licenced to drive 3.5 ton only. The weight of the vehicle includes not only 'fixtures and fittings' but fuel, water, luggage and passengers.
People are caught out time and time again by this. They buy motorhomes with high spec and lots of extras such as awnings and don't consider there will be little weight capacity for themselves and luggage.
2. Remember to make sure you have EVERYTHING you need in the van when you have parked up. It is no fun half way through cooking a meal to find you have run out of salt/loo roll etc and you are miles from the nearest shop. You can't just drive off with things lying around.
3. Storing the van - have you got a secure place to park it while you are at home?
4. If you intend going abroad, remember that you will be displaying UK plates and anyone and everyone will know that your passports are somewhere in that van. Be aware of security at all times.
5. Hire first! It may be an expensive holiday to hire a van for a week or two, but it will be a very worthwhile experience. You will find what you can live with and without, any other problems and give you experience when the salesman is schmoozing you into parting with a lot of money.
Here is a useful site that has a forum:
http://www.motorhomefacts.com/
Good luck!