Hi,
I highly advise you to acquire a Google Webmaster Tools and a connect that with your Analytics account to facilitate and monitor the change in your target audience. After you have set both up, here are the 2 main features that help to solve your problem:
1. Hreflang attributes. Google states at https://support.google.com/webmasters/answer/189077?hl=en
Many websites serve users from around the world with content translated or targeted to users in a certain region. Google uses the rel="alternate" hreflang="x" attributes to serve the correct language or regional URL in Search results.
Hreflang offers website or subpage targeting per language (English not French), country (so Australia not the UK). But note that it requires manually changing your site's mark-up.
2. Also of use is Country Targeting https://support.google.com/webmasters/answer/62399?hl=en
If your site has a generic top-level domain, such as .com or .org, and targets users in a particular geographic location, you can provide us with information to help us determine how your site appears in our search results. This improves Google Search results for geographic queries, and it won't impact your appearance in search results unless a user limits the scope of the search to a certain country. See a full list of domains Google treats as generic.
