You can put some citric fruit (orange and lemon) peels around your garden and it will deter cats. They dont like the smell because it irritates their nose.
Its not that its hard to find wood bleach, its the 2 part wood bleach that is quite hard to find. I have googled it and any place i found it being sold was either in america or the price was too high
Moss often grows on roofs because leaves that fall on the roof from overhanging tree limbs retain moisture. Copper sulphate works well to remove moss on roof shingles, especially when the moss is growing and rain is unlikely. You can use copper sulphate alone or a mixture of zinc and copper...
This is a link to an interesting article about how to make your own 2 part wood bleach and use it. It is quite hard to find wood bleach in the shops, and this method is cheaper to make.
http://mistralni.co.uk/articles/?p=238