Hi,
Dollar to Rupee currently 49.
You can check on this website http://www.xe.com/ucc/
I would take them you will have no problem changing them

Some exchanges may not take Amercan dollars as last april some Russians were trying to exchange fake $100
dollar bills, and some exchanges got caught out and refused to change anymore dollars.

If the dollar is currently worth 49 rupees and you got $2 per £1 you are getting 98 rupees for those pounds compared to the 79 you would have got with "current" ones ! You have to pay a commision on exchange whatever currency you use so you might as well use up the dollars ...unless you think the pound will slide still further.
I wish I had invested in a bundle of $'s for holiday money. Well done !