Everyone is eligible to shoot for county. In order to be considered county ask individuals to let county know how they are currently shooting by submitting their scores to http://hertsarchery.org.uk/content/ssf/. There are 4-6 matches per year and even relatively new archers can be competitive.
If you have questions then just ask. We will either answer or find out the answer for you.
Counties selection policy can be found here: http://hertsarchery.org.uk/content/selection-policy/