I'm British, so I'm aware of the erroneous labeling of Britain as England by others (particularly Americans), and vice versa. However, as Elizabeth was explicitly a leader of the English, it would seem inappropriate to label her civilization as Britain. Also, with the Celts in the game taking the names of Welsh, Scottish and (presumably) Northern Irish cities, it would pose a problem of overlap having the British (which must certainly contain Edinburgh as a city, among many others).
This is why I'm OK with the current situation.
We could either have had:
1) an English civ with explicitly English UA + UU/UB (such as longbowmen, and perhaps some UA bonus for great writers due to Shakespeare) and leader (such as Elizabeth or Henry VIII).
2) a British civ with explicitly British UA + UU/UB(such as redcoats, ship of the line and the current UA) and leader (such as Victoria or Churchill). Although this would have caused problems with the Celts city list.
3) a mix of the two, which obviously must make the choice of using the title England or Britain.
Currently we have 3), with the England designation. This eliminates the crossover of cities with the Celts, and also allows for a nice mix of cultural flavours of both Britain and England, which in turn adds more flavour to the game as a whole.
Edit: and sorry for going off-topic.