London is so vast I am forever coming across new hidden gems. Walking around the streets and getting lost is the best way to find London's best kept secrets.
The V and A houses a public collection of prints and drawings of every kind imagineable from old master drawings to photographs, playing cards, fashion plates and wallpapers. You have to select what you want to see from the collection http://collections.vam.ac.uk/and book in advance. The behind-the-scenes route up to the study room of v and a is a treat alone (pictured)
I have just recently finished a project installing a drawing for artist Alan Johnston onto the ceiling of the Tate Britain. The experience, although being somewhat taxing on peoples health with long hours and difficult working conditions was fantastic. The mediative and mind altering drawing practice that Alan has created combined with the enthusiasm of a team of talented individuals has resulted in what can be considered a great work of art. It will be open to the public later this year.
Quinto sells second-hand books. I spend a lot of time here and have found some inspiring books over the years, both at Quinto and the other shops on this road. Koenig Books on the corner is good for art books, too.