We have recently bought a second hand OKI C5200 Colour Laser Printer and even though the black and white print seems to be great the clour is coming out with coloured streaks, what would you recommend?

Shoot yeah Normtr is right. You have a bad image drum. Usually the color of the streaks indicate which color drum it is. An item located under the image drums called a belt unit lifts the colored image drums up when printing black and white. You will only see the colored streaks when you print a document that contains color. Putting a red period in a black and white document is all you need to enable color printing. You can swap the image drums around like Normtr said by pulling the guide pins off the left and right side for each image drum, then just swap the print cartridges around with the black and print a black and white document until you find which image drum is bad.

One or more of the drums may be defective. Swap the black with another color and print a document. If that color printed the charectors ok, then continue the test with the other drums each taking a turn in the Black drum position until you find the bad drum.