Ladybird, ladybird fly away home!!

I've got loads of blackfly colonising on my Turks Turban & Crown Prince Squashes.  I've squished tons of them but it's an uphill battle with so many huge leaves.  I then scooted round for ladybirds, found 5 and put them on the leaves.  I've done this before with my beans and the ladybirds immediately went to work, but this time they all flew off.  Is it the prickly undersides of the leaves they don't like??  I'm going to try a soap solution tomorrow but i'm not sure of the amount to use.  I've just experimented with a couple of teaspoons of Tesco's soap powder in a litre spray bottle and i think I've just killed a small  sage plant.  Any advice on soap spray recipes?

I use a small squeeze of washing-up liquid in a hand held sprayer - approx 500ml capacity.  That should get them.

If you want to beef it up there are load of options but one really handy one I was told is to spray nettle tea on aphids.  It strips off their outer protective layer and the sun shrivels them.  It does seem to work but the nettle tea is a bit smelly