Also would Scottish and Welsh people have used the terms interchangeably or would the distinction have been quite clear them?
EDIT: I was prompted to ask because of this Article from the outbreak of WWI entitled 'England declares war on Germany' which starts, "Great Britain declared war on Germany at 11 o'clock last night", using the names interchangeably.
Linda Colley is probably the most referred to historian on this British, English, Welsh, Scottish etc identity issue. Put simply she suggests that "British" acted as an overarching "umbrella" identity under which the other regional identities continued to exist. She claims that "British" only really became a relevant identity in two scenarios - Protestant agitation and (probably as a corollary of Protestantism) war with the French.
On the other side is someone like Keith Robbins who claims that "Britishness" was/is more of a compound of the various different regional identities of Britain.
As for the interchangeability of the terms "England" and "Britain", the general idea, so far as I understand it, is that the English never really had a national identity so would refer to themselves as "British" and imbue "English" values as being "British" despite the varying differences (perceived or real) between the peoples. Welsh and Scottish nationalisms would preclude such a scenario and would most definitely not use the terms synonymously.
This is my first answer on here so I hope it's acceptable. If this is something that interests you then this: http://www.york.ac.uk/ipup/projects/britishness/discussion/hardwick.html is a pretty good starting point for much of the "Britishness" argument. It contains most of the main historians that have written about the subject.
English and Great Britain have been two very different things. In the minds of many of the English England meant Anglican and everywhere else in the United Kingdom meant nonconformist (not Anglican) and this affected their language and rhetoric. This distinction is of course not clear cut since there were large nonconformist populations in the large industrial cities.
William Gladstone, who increasingly represented non conformists in Wales and Scotland couched his rhetoric in "Great British" terms. After 1880 he himself was the Scottish MP from Lothian until his death.
Disraeli (the conservative leader) on the other hand for the most part was attempting to appeal to the Anglican most of whom lived in England. He almost never referred to "Great Britain" only to "England".
Read DISRAELI AND ENGLAND by J. Parry and skip over the bits about continental philosophy.