Hi
Should I purchase localized urls like .co.uk or .com.au and point those at my .com?
This will not help you.
What are you giving Google to help them understand that your website is also for a UK audience? You need to provide flags for Google to understand or it will look at the major factors, e.g.:
- Name, Address, Phone number on your .com domain (are these US, or do you also list a UK address)
- Citations of these details ^ (are they cited on US based websites/directories)
- Server location (is site hosted in US)
- Domain registration details (US address)
- Inbound links (you mentioned 75% US, need more UK focussed + UK PR)
It's hard to give advice when I don't understand your business, but if possible, could you create localised versions of each page? i.e. www.domain.com (original) and www.domain.com/uk/ and www.domain.com/au/ (simple enough if site is built on Wordpress with the WP ML plugin).
This way your www.domain.com/contact/ would remain 'as is' but www.domain.com/uk/contact/ as an example would contain your UK address, UK phone number etc (don't forget you can buy postal addresses in most major cities around the world for ~£30/month).
You'd then build all your external UK links to your www.domain.com/uk/ pages.
One thing to beware of, this approach would only work if you could truly rewrite every page with unique content, which is much harder when it's EN-US to EN-GB or EN-US to EN-AU etc.
Do not copy the content from www.domain.com/product1 to www.domain.com/uk/product1 and think that changing the Americanized spellings to English will work for you. It won't! And you will risk a duplicate content penalty.
This is a good exercise, if done correctly as you'd be surprised how keywords change per country, especially long-tail phrases, even between English speaking countries.
Take vehicle rental as an example - van, truck, suv, rv, ute are all variations of pretty much the same thing, used across different English speaking counties.
Then the longer tail is more complex as American's are more familier with 'Rental', whereas English more commonly use 'Hire'. So if you're targeting one phrase only on domain.com and that phrase is suv rental, the guys looking for ute hire in Australia will never find you.
Oh -- You'd also need to implement href lang tags into your meta head to tell Google which version is for which Country.
Hope this helps.