Save yourselves a small fortune chaps, and use the 'system' recommended to me by a professional valeter ages ago!
Green mould? Milton's Sterilising tablets dissolved in warm water, scrub the solution in with soft brush, leave it a bit, rinse from open hose.
Clean with Johnsons blue (not lilac, different formula) baby bath mixed in warm water. Rinse as above. Do it twice.
Reproof when dry with the aforementioned Grangers Fabsil Gold applied with a 4" brush, which also has the effect of colouring the fabric, and looks natural, as opposed to something painted on. Apply a 2nd coat at 90 degrees to the 1st.
Bird crap on your hood? Pour cheap fizzy water onto it, the bubbles lift it out....rinse it away.
Pete