A splendid remedy I was told about recently by an old boy on the plot was rhubarb leaves.
Apparently if you put them in a bucket and pour boiling water on, leave to rot down you can use the rather smelly liquid on your veg and it prevents White Fly. I haven’t used it yet but as Rhubarb leaves normally end up on the compost hip you have nothing to lose.
Maybe you can let me know how you get on if you use it before I do? I will keep this page updated with how I got on though.