What time of year are you doing this?

If you go from late May onwards it's very practical to bivvy out overnight, that way you get maximum hours on the hill.

Re: the Bob Graham Round, it's do-able in 24hours but much more fun if you take 48 hours.

It's well worth taking a serious look at your footwear. A pair of good strong walking boots are fine, but do consider using trail shoes. They're MUCH lighter and if you get something along the lines of Innov-8 you'll find plenty of support....and they stick like **** to a blanket! Walshes are great but lack support, I certainly wouldn't consider doing more than 30 miles in them.

Good luck with your walk!

John