well, in general the chains rule the high streets; think starbucks, nero, costa. shoddy coffee, drowned in milk, sugar and syrups.
london has a few great coffee houses, but lacks the cafe vibrance that a city such as melbourne has. times are changing though. interestingly, the chains have started to implement 11oz flat whites!
the cost can also be substantial; between £2-3 per cup, last time . to the uk worker, that is significant portion of the wage (around £6p/hour is minimum, and therefore the wage for hospo workers!)
take advantage of the strong aussie dollar is my advice!