Just wanted to close this post off and say thank you to everyone for their help. I believe that the battery power issue is now resolved and I'll go with the 2 battery source approach so many of you recommended (9v for the atmega328 chip and 6v battery pack for the servos that consists of 4x AA batteries or 6x AA if they're rechargeable 1.2v batteries & I'll add a regulator).
I am thinking of changing the power supply now to a wall wart and add a switching regulator rather than using all these batteries, but I think I'll start a new post on that as that's a different topic from the original post 
Thanks once again for everyones help !