As a brit, I can honestly say theser names are just the norm. Some are vintage and are mainly used by 'posher' people and the others (I wwon't call them 'tacky' though they may seem that way) are used by the 'hip'.
I believe they prefer these shorter names (I dont see them as NN as you do) because to them its simple and cute.
Millie - There are plenty of little
Millie's running about the place. Personally I don't like it much, buts its sweet. I don't see them using
Mildred or
Millicent.
My friends cousins are called Millie-Ann Rosie-May and Billie-James...there mother is called
Tilly and their father
James (no joke.)
Evie - Cute, I like it but would NEVER use it, I prefer the full name
Evelyn.
Poppy - Not my type, but I can see why its popular here because of the war.
Libby - Not fond of this one at all.
Rosie - VERY popular, but I'm a
Rose person.
Rosie ages quite well here.
Demi -
Demi on its own seems normal over here and to me. People like its simple meaning.
Tilly - Not fond of this one either. I know a Miltilda but no one calls her that, she doesn't even write it as her name on documants, she uses '
Tilly'.
BOYS
Lewis - Again very popular, but this is not unusual at all!??
Alfie - A nice name over here, better than
Alfred.
My cousin is called
Alfonso but again they never use that name, they use
Alfie, all the time on documents, at school, etc.
Harvey - I don't like it, but its well used over here. No celebrities I'm afriad, they just like the sound.
Leo -
LOVE it!
Archie - Archer is strange to me. Not
Archie.
Finlay - Sounds Irish. I thinks its ok.
Harley - See
Harvey. But I like it.
Freddie - I don't see
Freddie as a nickname at all.
Frederick is just too much. Why use a name you don't like when you could use its shorter version which one does like.
Luca - VERY popular! Even in Italy, Poland. Its just a nice, simple name. Why shouldn't it be popular?
Ellis - Nice, but I know no
Ellis.
Zak - Again *breathes* to me I can honestly say I don't see a nickname. Its just a short name like
Ava. Could be short for
Zachariah though, that wouldn't be too bad.