You beat me to it violetblue as I had a tiny blue visitor yesterday. I wonder if it's the same one doing the rounds?
This one
http://i1.tinypic.com/23tf8di.jpg I believe is a male Small or Little Blue. It looks huge because I took it on a macro setting, but it's only about 24mm and is our smallest blue.
I don't know any that are extinct, but then I'm no expert. The Adonis Blue was down to just a few sites in the 1980's but is now gradually building up the numbers although still pretty scarce.