White bugs on strawberry plants?

Can anyone tell me what these are. And also what to do about them.
I have 6 strawberry plants that a got from Wilkinsons a few weeks back they are in pots in the greenhouse. All six have these small white bugs on them. Nothing else in the greenhouse is affected.

 

Whitefly. No honestly!, that's what they are called!

 

i have those bl**dy things over loads of things in my garden! flowers, mostly. pain in the bottom.