I started typing a response to this & after the 5th paragraph realised it was getting a bit long. I did a run from Stirling to Athens & back this year (to watch the olympics). Didn't take a haynes manual, and only one spare tyre (which was never used). We DID, however, have 5 litres of engine oil, slick 50 gearbox oil treatment, and about 10 litres of water along with a rugged toolkit (spade/axe/hammer/wrench), aircon, sufficient funds in travellers cheques and a couple of grand credit limit on the credit cards just in case. This, btw, is in addition to the 3 man canvas bell tent & kit to keep us comfortable camping for 4 weeks. The furthest driving day was 540 miles, and the longest driving day was 150 miles - got caught in traffic entering switzerland & spent 6 hours travelling a 10 mile stretch. The German red cross were handing out plastic cups of carbonated water to people stuck in cars. Since we got back I've been meaning to put the whole story together for a blog or something, we even kept notes.
Choose the right car. Suitability is key, theres no point taking a 25 year old vw camper on a trip around the world if you can't tell the difference between a dodgy spark plug and a dodgy timing belt, and old defenders aren't that much fun when you're expecting to drive 500+ miles per day either. We took our Discovery commercial, and it was perfect (if a little slow & cumbersome for the Italian B roads), but I couldn't have managed it without someone in the passenger seat watching my blind spot & navigating for me with the small library of maps we took (GPS fails most often when you need it most, and sometimes it tells lies about the quickest route :yikes: ).