You're in England. OS maps are among the best in the world, and the distances from East Anglia to the Lizard are small enough that you could manage perfectly well with a couple of maps.

Navigation is not really a problem. Look at the maps before you start. Check out the areas you want to avoid - greater London will probably be on that list - and figure out roughly how you are going round them, through Hertfordshire and Buckinghamshire for example. Then you have a choice. You can draw up a route in great detail, planning in advance exactly where you are going to stop each night, or you can sketch out roughly how much ground you need to cover in the time you have available, and improvise. The latter is usually my approach, I prefer to have the freedom to spend extra time somewhere I find appealing, or divert to look at something of interest that someone has told me about, or whatever. If you are camping, it is frequently possible to simply ask a farmer if you may camp on the fringes of a field or whatever. If you want to spend a few quid for greater comfort, youth hostels or B&Bs. Hostels have excellent facilities these days, though obviously they aren't going to cost £5.

Bear in mind that you are on a bike and can cover a lot of ground. If you miss a turn or get lost for a half-hour, that is not a disaster. The worst that is likely to happen is that you have to ride an extra twenty miles that day to get where you wanted to go. That's pretty trivial. As your confidence increases you may even forget about having a detailed route, and just head off in the general direction that you want to go. This is especially easy to do in England, where there is such a dense network of minor roads signposting is pretty good, and nowhere is very far from the next settlement.