Thanks for replying so quickly – it's greatly appreciated.
Yes, I am seeing a different version when previewing before the test. When I preview version 1, the heading content reads 'Header A'. When I preview version 2, the content heading reads 'Header B'. This is acting as it should.
When I click 'publish site' then go back to preview versions 1 and 2, both versions 1 and 2 have 'Header B'.
Please note that I'm sticking to a page test even though this basic content testing. Why? In basic content testing, when I preview and test, both versions 1 and 2 show 'Header B', even though version 1 has been set up with 'Header A'.
Make sense? More than happy to explain more if need be.
In regards to caching? I'm assuming these are what you're referring to?