This was one of the threads I was thinking about, though I think there were others. There's a few links in there. There's other stuff like that floating around the 'net and elsewhere, as well.
I'd probably imagine there'd be at least some modern tools in the box. Small crank generator and a netbook might take less room than paper et al, and if you can get some other means of data transference (paper, stone, whatever.) going in short order you could probably transfer a
lot over to more lasting mediums before the electronics in it failed. Providing you did that, you might be able to fit in a nice little cache of jump start equipment.
Even if you did go with paper, something like the EB would probably be a bad idea -- there's a lot of stuff that wouldn't be very useful in it, and space is your primary resource. You'd ideally want texts based on the current state of various fields (chemistry, metallurgy, agriculture, etc., so forth, so on), with an emphasis on theoretical procedures on how the point was reached and how to go forward. And usability in a low tech environment, of course. Probably not written in english, to boot... some kind of cypher (shorthand, etc. Might be able to get really fancy with that and have texts that provide different information depending on which cypher you filter it through.) or a more concise language would be ideal (again, space!). Then maybe a bit extra in regards to ethics, etc. History would be kinda' useless, but fiction scenarios constructed both for readability and to highlight whatever values you end up going with would likely be ideal. You don't want to lose universal literacy, so making reading as interesting (and useful) as possible straight from the start is probably a good idea.
Government wise, it's kinda' hard to say. Most of the issues that sort of thing addresses isn't going to pop up until you've actually got a population large enough it becomes necessary. S'a long term, generations away (many generations if you're handwaving away the inbreeding thing, as it'll take a while to get a notable population going with a five person start, even assuming nothing buggers up along the way), issue. Dealing with that would be... tricky. My personal likely suggestion would just be to start and foster a heavy tradition of ethics, logic, and solid rhetoric, and see if the problem can't solve itself. A highly educated anarchy-type thing (there's a term for it that I'm forgetting, but whatever. Enlightened, maybe?) might be an interesting experiment.
Idle considerations: You might want to start out further south than Britian. A milder winter'd make it less likely you have trouble making it through that first few years. Critters aren't really gong to be an issue if you bring along a knife -- spend the first day carving out a few javelin throwers and fire hardening some sticks and you've basically ended any threat the animal world presents, to say nothing of the dozens of other tricks our species figured out when we bent the varying parts of the world over our collective knee. Real issues are disease (this might be a big one, dunno) and vermin of varying sorts, not larger critters.
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