Okay, well in that case - don't worry about the lack of contact (yet). I know very few tutors who would prioritize maintaining contact with a student who hasn't officially started yet (unless the two of you had some kind of agreement?); indeed, in my experience contact dribbles to a halt over the summer anyway, even if you're entering an anxious fourth year of your PhD. I've had no communication with my current supervisors since early June, and don't expect it to resume for another couple of weeks at least (AND I have my 'upgrade' looming very soon). If you suspect that he's the hands off type generally though, and that the unresponsiveness will continue into your first year, then it would be an idea to ask him outright how much contact time he prefers with his grad students, and to articulate your preferences, and to work out a compromise. But my main feeling is that you needn't be worrying about this now, because it would seem quite unusual (to me and the tutors / grads I know at least) to be in regular contact before you've started. As for your prep research - try not to get ahead of yourself. You generally have your whole first year to devote to sleuthing and preparation, so there's no hurry, and tying yourself up in knots now won't help. Nor will accumulating too much information before you have a tighter sense of what direction you're heading in - and this is bound to meander a bit in the first year (this bit of advice may be subject-specific however; obviously I don't know much about how to go about a history thesis, and you undoubtedly know a great deal about this, so please ignore if it's irrelevant). It's good that you're so enthusiastic, but as you say, if your 'shedload of work' turns out not to be as useful as you'd hoped, it can be disheartening and lead to a premature slump in motivation. I had this problem, and I think my first year has been kind of choked by it.
As for theoretical differences between you and your supervisor - everyone has this problem to some degree. My ex-supervisor and I got on wonderfully, but there were many times when our different theoretical positions, or even just basic understandings of the topic at hand, crashed head on. This is where your Oxford-honed ability to argue your case comes in handy! Of course, it's a difficult balancing act in the student-supervisor relationship to respectfully disagree with your supervisor's position, stick to your guns about it and, despite their seniority, prowess and (initial) superior knowledge (if not of the subject itself then at least of the ways in which one goes about writing a long thesis), to persistently and courteously ignore, or at the most, footnote all of their arguments, while somehow still deferring to them, depending on them, and not putting their nose out of joint. In the end,it goes back to the email my supervisor wrote me: "the real game is one in which you use your talents to courteously, almost imperceptibly turn the tables and begin teaching them. Once they get to be YOUR students we give you a Ph.D." This will happen whether they agree with you or not, so long as the thesis is sound. Gone are the days when you have to agree with the marker to ensure a First; this is YOUR thesis, not your supervisor's. Mine had a habit of saying 'IF this were my thesis, I'd do this instead of that...' - so I suppose whenever your supervisor disagrees on a theoretical issue, just mentally prefix whatever he's saying with 'If this were [his] thesis ... but it's not'. Obviously don't do this with all his disagreements (!), just those that stem from any fundamental theoretical differences you have. And that's not to say his disagreements won't be useful - c.f. Boosh's post - just that you have to separate the useful, productive arguments from the distracting, potentially derailing ones.