A minimum of 12" diam/ square!

See here;

http://www.thegardenersalmanac.co.uk/Data/Figs/Figs.htm

One that the tree will just fit in comfortably now. As the tree grows then re-pot in a size larger.

Thanks for your help - it is much appreciated,

I was told when I bought mine that they didn't like too much watering either

Thanks for your point about watering. It has been a problem this year!