I've never heard of a guide offering the sort of route you're looking for, which sounds like a great idea, by the way. So, what you'll have to do, if you're unfamiliar with the area, is track down whatever you can, read up on as many routes as possible, then make some attempt to join up the ones that are running in your general direction. Of course, you'll find gaps between them, and those gaps may be huge. At that stage, you can only rely on what the map is telling you. It will tell you where the rocky and boggy bits are, and how steep the ground is, but it won't tell you if it's knee-deep heather or brambles! When you put your plan together, you probably won't know if your intended wild camps are going to be OK until you actually reach them, in which case you may have to keep walking. Also, unless you're going to carry all your food, you need to make sure that your route passes any shops along the way. Water, on the other hand, shouldn't be much of a problem.
