The best thing about any charity shop is that you never know what you are going to find. I have a well tested route around London that includes all of my favourite charity shops. This Oxfam has a great selection of books and often turns up some interesting clothes too.
I've only just discovered this fantastic little salad bar-come-florist right round corner from my studio. It serves freshly made salads that are not only delicious but cheap too! Either take away, or grab the one and only table and eat in.
I love how much you are aware of the changing seasons out of the city; there are numerous beautiful forests around Hertfordshire to go for a run, a walk or have a picnic. One of the best destinations for a day out from London might be Northaw Great Wood. The main entrance is located on the Ridgeway, the B157 from Cuffley to Brookman's Park.
They describe themseleves as a 'village shop in the City' and sell everything 'typically english' you could dream of, from homemade scotch eggs to english meade, this tiny shop is the reason I cross the road early every morning, just to see what treats they've got in for the day.