I have been colouring my hair for 4 years, I have used all different colours of reds, and now I am getting bored, I want to go to a medium brown, How do I get rid of the red out of my hair?

Is it red tones or more orangey tones you're trying to eliminate? If it's orange tones, you could try Goldwell Colorance (which is a demi-permanent color) in #6A, which is dark ash blond. It has a blue-ish base which would counteract orange. If its red you are trying to get rid of, you could mix this with something with a gold base like a 8G or use mix the 6A with some Goldwell Gold Mix (the gold and blue undertones mix to create a green undertone, which counteracts red).