Hey @debharrison,
I just wanted to jump in and let you know, I’ve recently released a new custom extension for HivePress that includes the ability to restrict the locations Users are able to choose from.
If you decide to check it out I’d love to hear any feedback you can offer - and, if you have any ideas to improve it, or encounter any bugs - just drop a reply in the relevant topic, and I’ll try and push an update out as soon as possible! 
Cheers,
Chris 