Can't wait for the cherry season! Though they don't have them here in London in abundance as where I grew up. Living in London one can miss out a bit when it comes to seasonal berries and fruits - they just don't show up that often and on time - even in the better supermarkets.
One way around is to go to a farmers market that have been popping up more and more since I moved to London 10 odd years ago.
I used to work very close to the now famous Borough Market (near to London Bridge) and go to have lunch there quite often on a Friday- I loved Brindisa's Chorizo Sandwich.
The market has a lovely atmosphere, lots of stands to get inspired by for the weekend, but cheap it ain't. Restaurant Chefs tour it with special clients, cooking schools can be found drooling over vegetables and spices ....
On a Saturday you can also find us cycling to Barnes Market, which is not very big, but has a good variety of stands including a fish monger and is situated opposite Barnes Pond, a lovely spot to have a sandwich, feed the ducks and kick a ball (and there is also a nice climbing tree!)
Here you can find a wide choice of London markets and organic markets you will find here. Enjoy and happy hunting!