If I get a blister, I always find that sticking the offending foot in a cold beck and then, once dry, treating with compeed, works a treat. Something about increasing blood supply, probably. Anyway, freezing water is always soothing for some reason.
I think its perfectly possible to do this route at this time of year, although, if there's proper winter conditons, it might be hard doing it in the time. Inevitably, if you're going to take 10-ish hours, some walking would need probably need to be in the dark. A pre-dawn start should sort this out, though. I think Wainwright's worries probably centre around limestone country under deep snow - ie the technical possibility of falling throught he snow into a pothole or a clint (or is it gryke?) As far as I'm aware, the only time something similar happened was a walker on Cross Fell who fell through snow down a mineshaft a few years back. Under normal conditions, this is probably a bit unlikely.
Whilst I agree with the comments about fast-flowing, bubbly water (and add that its much safer if its been filtering through gravel) - the main problem with having nice, sterile tap water to drink at home is that you dont get a natural immunity to drinking what amounts to diluted crap. Personally, Ive been drinking crap (and that includes Boddingtons and beer with the word "smooth" added) for 40+ years and with little adverse effect, other than a slight squint and a belief that God is alive and well and living in an allotment shed in Newton Aycliffe. But I wouldnt trust lake District water as far as I could chuck it, as the whole place is grossly overcrowded with incontinent walkers. Crap, boiled or not isnt really all that appettising when mixed with beanfeast and/or pasta shells. I'd rather consume Stanley the Stag's boiled poo soup than the bowel contents of a middle class Cheshire housing estate any day. But you cant carry eleventeen gallons of water with you can you? (I'm talking a three day trip, here) If its green and smells of wet dog - dont even drink it boiled.
Smashing idea for a jaunt... I've done a few chariddy things (dont like to talk about it) and I always have trouble getting sponsors - its getting a bit old hat being sponsored I think. Last time we did a charriddy walk (dont like to talk about it by the way) - we asked people to buy a guess at how much liquid would be consumed by the walking group on a 35 mile walk in summer. We got a few prizes donated (a Kodak camera from Kodak,some bottles of loopy juice and so on ) and guesses were a quid each. Anyway, we raised £250 for a diabetes blood machine thingy for the hospital. People responded better than just coughing up some dosh. A bit of imagination about the fundraising could be very lucrative.. Other than that it should be a good trip. Where on earth do you get the time?