"salvos" - Salvation Army Opportunity Shop.
In Australia R20's sell on ebay between Aus$50~$120 every month or so.
Before you rehabilitate that bike, price your parts because its going to break your heart or your wallet.
And theres always some poster who will say, "but for that money you could have bought a...."
If you haven't done some searches already check out http://www.flickr.com/search/?q=raleigh+twenty+&m=text and you will be Lost in Love (thank you Air Supply).