5'2" hourglass size 10 here. Pretty much in proportion so petite clothes tend to fit very well.
Tops I generally wear from the normal ranges unless it's a very fitted shirt. I wear a lot of 3/4 sleeves. When I do buy a petite top I really notice how well it fits, I've got a lovely fitted tweed jacket from Boden that fits like a glove.
Dresses I pretty much always buy from petite ranges (another vote for Boden although I think they cut more for a pear shape so there's not as much room for the bust as I'd like), got a gorgeous cotton shirt dress from Precis of all places in the summer. Coast have a small petit range. But for looser styles I'd go for minidresses because they tend to be respectable lengths on me (just bought one from COS actually).
Skirts I buy minis or maxis. Anything inbetween are frumpsville.
Trousers or jeans pretty much always need to be petite: Boden, GAP, M&S, NEXT, Mint Velvet, ASOS, Boohoo, Anthropologie, Topshop, DP, all have short trousers.
Ages with the PP about ordering online. I prefer it to be honest, I can try things on with a range of other clothes from my wardrobe and it helps me plan. Paying up front is a pain though I do agree.