Hi,
I have now solved my issue. I had to move the desktop PC from the bedroom/study it was in because we needed the room for guests. I decided to put it in the lounge attached to our Smart TV and got rid of the Acer monitor I had been using. It works great on the TV, and it serves all the functions we previously used it for! It looks like it was an issue between the graphics card, drivers and monitor - I've still no idea what the exact issue was, but the irritation it caused has stopped now