Be sure of what orice you should be paying, do loads of research. There are loads of private sale cars on offer at very close to dealer prices and you loose any comeback if you buy private. You really need to be sure of what you are buying if spending decent amounts of cash.
HPI check is an absolute must. I would do that before even viewing as you may be wasting your time doing it the other way round. Its shocking how many cars do not come back HPI clear, sometimes there are genuine reasons for this but best to have the knowledge upfront.