You learn something new every day, while trying to ID this Aphid type it came to light that these have been mummified , in each one is a Parasitic wasp larvae which will emerge fully developed.
Natural enemies are various species of parasitic wasps that lay their eggs inside aphids. The skin of the parasitized aphid turns crusty and golden brown, a form called a mummy. The generation time of most parasites is quite short when the weather is warm, so once you begin to see mummies on your plants, the aphid population is likely to be reduced substantially within a week or two.
I have just been out to check and sure enough here is a photo I took of the empty bodies and you can clearly see where the wasp has emerged from mummified aphid body.
Today I found the wasp that parasitise the Aphids