Not the most exciting place inside, but a lovely rooftop area which not all that many people seem to know about, 2 mins walk from Old St station. If it’s packed then The Red Lion is just up the road.
They mainly sell art and cultural theory books but they also have a good selection of small press and self-published zines. It’s a great place to browse and get ideas.
Cordings situated in piccadilly is a renowned establishment for British Country clothing and tailoring - that can not only kit you out to shoot pheasant in the finest yellow ochre cords but for me offers a great selection of socks.
The second coffee shop has to be Kaffeine. Having only recently come across this one, I was certainly impressed and they may even have the best coffee I've had, since a short stay in Portland, Oregon.
The Greenwich Observatory with its green laser beam can transfigure any night sky. If you decide to cross the Thames via the foot tunnel, make sure you look out for the green ray. You can be on one side of the meridian in a minute, and cross to the other side on the next, without even realising it.