Mum's nimbu pani recipe gets a lovely write up:
http://www.guardian.co.uk/lifeandstyle/wordofmouth/2012/aug/09/how-to-make-perfect-lemonade
I love this drink myself and made some this morning when I took Grandma (John's mum) out for a picnic. When making for myself, I use sugar-free, instead of sugar. This is the drink that is offered at most Indian homes when someone drops in during summer months. It is so thirst quenching.
Congratulations. It was indeed a pleasant surprise to see the link to this site.