If you camp, you will be slower: extra weight to carry, and it takes time to pack up in the morning. But it will be cheaper - you can usually camp for £5 - £8, and often for nothing. (Wild camp in the Scottish hills, Forest of Dean, Exmoor etc. A green tent helps. Or find smallholdings and "dog and stick" farms and knock on the door - the worst that can happen is someone saying no).
Mrs Uncle Phil and I did this. Our biggest expense was the train fares. I think it probably cost us £300-odd each, and at least £200 of this was train fares. (Not including food, but then you have to eat anyway, right?) We had two youth hostel nights, and didn't eat out at all (although we did have one or two beers and coffees. Not many, though).
Oh, and high mileages on crap roads with camping luggage is hard on tyres, rims and spokes, especially if you're on the large side. Use your Galaxy if you camp.