Kate H.
Yelp
This is my go-to flower shop. Well, not even a shop really... it's just a little stand just east of Portobello Road Market. As is to be expected, the flower selection is best in the morning and on non-market days, when everyone and their dog seems to find it romantic to pick up a bouquet during their market shop.
They carry an array of beautiful flowers throughout the seasons, often including unusual succulents, herbs, and even thistle and wildflowers, and will happily sell you a few stems of your favorite hydrangeas or tulips. But they shine in the arranging department as well. I recently had them put together an autumnal bouquet for my dining table. It was made up of rust and yellow dahlias, a lush purple wildflower, and springs of rosemary. It lasted more than two weeks!
It can be a bit pricy (I paid 30gbp for the large bouquet mentioned above), but it's excellent value for money. And I don't say that often in London, and especially not of most of the businesses near Portobello Road Market.