Posted: 16/04/2015 at 02:15
The only thing which will likely work in the way you want is to introduce a whitefly-specific predator. Encarsia formosa is a tiny wasp which will prey on them. Eretmocerus Eremicus is another similar wasp. You may need to try both.
Most of the common predators such as lacewings, ladybirds and hoverflies predate on aphids, not whitefly and will ignore them.
The whitefly predators are only effective when it is warm enough and are normally used in greenhouses as that is where most whitefly infestations occur. As you are in Brighton there is a good chance that these will work outside in a few weeks time when night-time temperatures are higher and more stable, especially if your garden is sheltered. There are several online suppliers.