The first two are common blue, Polyommatus icarus.
And you are correct about the second two: brown argus, Aricia agestis.
There is very good guidance on separating these two (and other) species on Peter Eeles' et al's excellent resource on British butterflies
Thanks for your quick reply to my images,also for the link to uk butterflies website which i will have a look at.
I take quite a lot of butterfly photos ( weather permitting ) mostly i can id from guide book, but i find some of the blues quite difficult.
Just be grateful - the blues are.easier in the UK than on the continent!
Considering all UK butterflies, not just blues...
There are usually little features that can be used as differentiators; the UK Butterflies web site'll help in that respect. In fact, they have a special page for just that - http://www.ukbutterflies.co.uk/species_similarities.php. There are a few pairs they are still working on, but nonetheless I have to say 'great stuff'.
The key features can be on the uppersides, undersides or elsewhere (tips of the antennae re Essex and small skippers). So I suggest you take photos from as many angles as possible. Even if some of them are poor photographically, they can make all the difference when it comes to naming.