No affiliation with any of the vendors. They are small shops that ship to the EU, where I live, and I think of them as curators more than sellers. Their tea shaped what I like. Many of the teas I loved have since sold out, so the ones below are the ones you can still buy.
Mei Leaf
London. I have been drinking their teas for years. The range is wide and the quality is excellent.
For aged white, the Jade Star series of aged Bai Mu Dan is spectacular. For oolong, you can't go wrong with their Dan Congs; Butterscotch Temple is delicious, and the GABA oolongs (Tiger Eye, Amethyst) are worth trying. For black, Cocoa Malt Queen, a Jin Jun Mei. For green, Monkey Picked and Long Jing Supreme. For young sheng, the Young Gushu series. For shu, Nug Potion.
Their YouTube channel is a lot of fun and is where I learned most of what I know about brewing. TeaDB is the other channel worth your time.
white2tea
Run by an American who moved to China and has been pressing puerh there since 2013.
I have mostly tried their shu and love most of it. Start with Gina and Loon-Call in the Dark. To splurge, Reckless Daughter or Reading Room. Get several samples before you buy a cake.