Thanks for your replies, its interesting that the advice is fairly consistent ie., about 110-120 litre.
Currently I have a 5.3 Neil Pryde Zone sail, and am thinking of upgrading to a 6.5 soon. I will probably go up to a 7.5 sail later as well, depending on the economy.
I am situated on the East coast of Australia in Brisbane, which has inconsistent winds between 15-30 knots but it can go higher.
I don't know what else to say except that I'm 56 and dont expect to become a wave sailor, but will stick to flat water.
Any more advice would be welcome!!