There are many on the market and some are sold under different names but are the same. I use: http://www.totallywicked-eliquid.co.uk/ They are very reliable and a good price.
The one I have is called the Tornado. The battery lasts about all day. Many people smoke & use the e cig and others switch totally over to the e cig like me. The ones you get from the chemist aren't very good and shouldn't be compared to the ones sold at this place.