OMG! – I’ve found the cause of the flickering issue!!!!!!!!!!!!!!!!!!!!!!!!!!!
It’s because I have the Raleway font already installed on my system and I’m also using the font on the site, this was obviously confusing the browser as it didnt know whether to load the web version of the font or my local version!!!. After deleting Raleway from my system the flickering has stopped!!!.
Werhoooooo! 😀
Now just to work out the cause of those lines of the nav bar when hovering over it, although I feel this will be even more difficult to diagnose.