Moss, Algae and weed killer. Only for use as a home garden weedkiller.
I just bought Weedol 1L Weedkiller for £3.99 at Wilkinsons. The spraygun has a cardboard collar offering £1.50 cash back. You just fill in your details on the inside of the collar and enclose the receipt with the item circled. Offer valid until 31.12.10 and it doesn't say you can only apply once.