I presume that the route is along the fairly standard Donald Hirsch route. I did this last year unsupported and it was great fun. The only part I didn't like was the London to Brighton part that's not really on his route, but that was probably more down to my lack of preparation for that part of the route.
There's plenty of advice on his site about accommodation and it's mostly very high quality and reasonably priced. I can dig out where I stayed if you want.
I'd love to do it again, but would have to question the value of the £300 + £1,000. If I wanted to raise money I'd be tempted to do the route on my own but raise charity money as well.