a common garden greenfly spray should kill them. If you have only pot plants, you could buy a 1 litre spray bottle at any hardware shop or larger supermarket. Own-brands are usually cheaper. Yours look a bit slim for aphids, but the common spray should work.
If you have a garden, especially with small trees, it would be worth buying a bottle of concentrate and a pump-up sprayer.
For anything that you intend to eat, you can get fruit-and-vegetable sprays that are less persistent.
If you have roses, you can get "Roseclear" which is a combined fungicide and insecticide and also treats black spot, mildew etc which they are prone to. I use it on most small ornamentals, not just roses.
If you're lucky, local bluetits will feed them to their babies. I would avoid chemicals because of this, i.e. the insecticide will also kill all the other baby bird food and this is exactly the wrong time of year to do that.
Aphids are easily squashed, they don't run away very fast.
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