Government legislation has resulted in many chemical treatments that were once available to the 'amateur gardener' being taken off the market.
Some products that are still available may require a 'users licence '
Due to this the writer has refrained from naming any particular chemical treatments.
Here are a few addresses where you might be able to resolve your problem/s;
http://www.rhs.org.uk/Gardening/Help-advice/Garden-chemicals-and-pesticides
http://www.garden-care.org.uk/content/g_home.aspx
http://www.pesticides.gov.uk/
http://www.just-green.com/