Feels like time this is updated, always useful to have a list of high quality coffee shops dotted around town so visitors or locals can always work out if they're in striking distance. I'd certainly appreciate some recs for the areas I don't know as well so please feel free to expand.
I've deliberately left out of the food offerings so as not to over-complicate but most of these places also offer excellent sandwiches and light meals.
Workshop Coffee - same people behind the Melbourne place. Probably the best in London (although don't go if in a rush)
Dose - even closer into the City/St Paul's high quality place using Square Mile beans.
Department of Coffee - another antipodean place on Leather Lane by Hatton Garden. Superb coffee from Climpson and Sons. Also run barista classes in the evenings which are highly recommended.
Prufrock - Opposite Department of Coffee and slightly inferior but good for variety.
Shoreditch Grind - on silican roundabout itself by Old Street. They use their own evolving blend.
Allpress - superb place with its own roastery from which you can buy takehome coffee.
Climpson and Sons - Broadway Market in Hackney. I've never actually visited this place but given the quality of Climpson's own coffee I can be pretty certain it will be very good.
Caravan (branches at Kings X and on Exmouth Market in Clerkenwell). Another place with its own roastery which supplies a number of high end restaurants as well including St John. Rotating interesting filter selection which will often offer a Yirgacheffe as well as a darker nuttier coffee from Indonesia with plenty of Latin American as well. Service can be questionable.
Fred & Fran - long way out in Stoke Newington but superb little shop brewing Square Mile Red Brick. Not worth a trip but if you happen to live/visit the area highly recommended.
The Little One - another neighbourhood coffee place at the east end of Primrose Hill. Not really space to sit unless it's a nice day but another good quality espresso place using Square Mile.
Speakeasy Espresso - Uses the coffeesmiths espresso blend but also offers a variety of brewed coffee. Just off Carnaby St a good choice in what can be a quality vacuum.
Monmouth Seven Dials - Main shop for Monmouth Coffee where the queues are shorter than at Borough Market. Lots of coffee to takeaway as well as their traditional filters and espresso too (although espresso is a bit of an afterthought here compared to the Aus and NZ places).