There was a thread on this not too long ago. If you look back for 'Steripen water purifier' (or similar).
Personally, I can't stand Iodinised water. I've tried using neutralising tablets with Iodine to get rid of the taste, but it didn't work. I find the major problem is that because you come to dread drinking, you don't so you get dehydrated.
Having said that, The Ridgeway isn't exactly the wildest of LDPs is it? I'd be surprised if you had to walk so far between potential water sources that you'd need purification, and knowing the Chilterns well, you'd probably find it easier to get water by stopping at the local pubs for a pint, and filling up while you're there. There's also plenty of farms on/near the route and I don't suppose they'd be too annoyed if you asked if you could use their outside tap.
S.