Good for you Celia, you wont regret it. I did this trip in November 2014 (without the add-on) and it was truly memorable. A lot of early starts but SO worth it. The weather then was warm without being too hot but fleeces/cardis were needed for the early starts but soon discarded. Agree about the 'holiday tummy', take some immodium or similar with you. I had it for about 24 hours but it didn't spoil anything, just fasted for 24hrs with plenty of water & it was over, some people on the tour didn't suffer at all. Varanassi was a highlight as was the Taj Mahal but the highpoint for me was seeing a Tiger on two of our game drives at Ranthambore (which brought tears to my eyes). Hope you have a wonderful time!