Thanks for helping me out.
I manually installed the Wordpress Health Check and Troubleshooting Plugin
This showed me that updates were being blocked or more specifically;
"Error A plugin has prevented updates by disabling wp_version_check()"
So It turns out that there were two new lines added to the end of my wp-config.php.
I deleted these lines and boom, instantly the plugins and Core update was available, I ran all the updates then installed WordFence, When I ran WordFence it found out the site had been hacked and there were over 20 files that needed deleting and that sort of explains what was going on.
I deleted all the themes I wasn't using, seems that is how the hack was carried out using an outdated theme.