Edit State/Province Field

We are based in the UK and have absolutely no need for a State field, however since we have recently collected quite a few US customers we have had to activate this field since US customers attempting to make a payment via credit card were receiving error messages due to not inputting a State.
This, however, is now causing problems with our UK customers getting error messages since we do not have state or province details to add in this field. The problem is that the state field is also a required field and if something is not added this will cause error messages regardless of the customers origin.
In an attempt to try and make this a little smoother for our customers and at the same time not completely refuse cc payments for our US customers we simply wish to make a small edit to the displayed text for this field.
We simply want to change the State/Province field to - County/State.
Could anyone please provide any support on how this can be accomplished?
P.S We do also have the quick and easy, single page checkout add on installed. I do not think this makes any difference but wanted to mention it anyway. Our website can be found in the footer of this post. Thank you

Iv found - define('ENTRY_STATE', 'State/Province:'); on line 230 of my english.php file but did not want to just edit it to County/State incase it killed the connection with any other files required to make the function. I obviously do not want to cause any error messages during customers payments. Does anyone know how I can accomplish this without causing any errors?

Looks like iv stumped everyone !!!

Go ahead and change that define value to what you want it to be. Since that only affects that text, it won't have any effect on any function.