using the scanner to import the image into the computer i clicked the 'details' button to select the area to import from the scan into the computer rather than scanning the entire A4 sheet.
after than using either the eyedropper tool or typing the numbers in the gbr scales to the colours wanted (as most of them were greys and blacks) i then using the polygon lasso tool to select linear parts of the image and then using the set swatches i used the fill tool to block in the areas