Thanks will keep an eye out for that.
Still trying to do some of the other suggestions, but a common issue just happened again right now.
My back office login had timed out so I was on the screen with the photo to the left and the sign into Umbraco button on the right, past experience tells me clicking that button has a high probability of not working, so I edited the url to remove the /logout from the end.
When I then hit enter to try and access the back office, which should then represent the login screen. At this point the browser tab started just spinning, at the same time the front end of the site also stopped working and started spinning if you tried to navigate to any pages. Only once the back office login page had loaded, did the front end become responsive again and the page loaded, it took around 30-40 seconds for this to happen.
They have multiple staff using the back office throughout the day, so if this is happening to them I can see why we get random hangs with no clear reason.
Have not managed to get to the bottom of why that is happening, but its very consistant from my experience.