N. V. Tatsenko introduction to theoretical phonetics of english

BBC
GA
'car'	[ka:]	[ka:r]
'more'	[^m0^:]	[mo:r]
’fear’	[frn]	[fir]
'care'	[keo]	[ker]
'tour'	[too]	[tor]

American vowels followed by [r] are strongly "r-coloured", to the extent that one often hears the vowel at the centre of a syllable as a long [r] with no preceding vowel. The GA vowel in 'fur', for example, could be transcribed as [з:г] (with a transcription that matched those for the other long vowels in the list above), but it is more often transcribed with a diacritic ^v to indicate that the whole vowel is "r-coloured". Similarly, the short "schwa" in GA may be r-coloured and symbolised [э¹" ] as in 'minor' [mainre¹" ] . It would be wrong to assume that GA has no long vowels like those of the BBC accent: in words like 'psalm', 'bra', 'Brahms', where there is no letter 'r' following the 'a' in the spelling, a long non-rhotic vowel is pronounced, whose pronunciation varies from region to region.
One vowel is noticeably different: the [o] of 'dog', 'cot' in BBC pronunciation is not found in GA. In most words where the BBC accent has [o] we find [a:] or [э:], so that 'dog', which is [dog] in BBC, is [da:g] or [do:g] in American pronunciation. In this case, we have a phonological difference, since one phoneme that is present in BBC pronunciation is absent in American accents. Other segmental differences are phonetic: the [1] phoneme is almost always pronounced as a "dark 1" in American English: the sound at the beginning of 'like' is similar to that at the end of 'mile'.
The pronunciation of [t] is very different in American English when it occurs at the end of a stressed syllable and in front of an unstressed vowel. In a word like 'betting', which in BBC pronunciation is pronounced with a [t] that is plosive and slightly aspirated, American speakers usually have what is called a "flapped r" in which the tip of the tongue makes very brief contact with the alveolar ridge, a sound similar to the [r] sound in Spanish and many other languages. This is sometimes called "voiced t", and it is usually represented with the symbol [t].
There are many other differences between American and English pronunciation, any of them the subject of comic debates such as "You say tomato [ta'meitao] and I say tomato [ta'ma:t3u]".
Scottish. There are many accents of British English, but one that is spoken by a large number of people and is radically different from BBC English is the Scottish accent. There is much variation from one part of Scodand to another; the accent of Edinburgh is the one most usually described. Like the American accent described above, Scottish English pronunciation is essentially rhotic and an 'r' in the spelling is always pronounced; the words 'shore' and 'short' can be transcribed as [for] and [fort]. The Scottish [r] sound is usually pronounced as a "flap" or "tap" similar to the [r] sound in Spanish.
It is in the vowel system that has the most important differences between BBC pronunciation and Scottish English. As with American English, long vowels and diphthongs that correspond to spellings with 'r' are composed of a vowel and the [r] consonant, as mentioned above. The distinction between long and short vowels does not exist, so that 'good', 'food' have the same vowel, as do 'Sam', 'psalm' and 'caught', 'cot'. The BBC diphthongs [ei], [эо] are pronounced as pure vowels [e], [o], but the diphthongs [ei], [ai], [oi] exist as in the BBC accent (though with phonetic differences).
This brief account may cover the most basic differences, but it should be noted that these and other differences are so radical that people from England and from parts of lowland Scotland have serious difficulty in understanding each other. It often happens that foreigners who have learned to pronounce English as it is spoken in England find life very difficult when they go to Scotland, though in time they do manage to deal with the pronunciation differences and communicate successfully.

3. 
   Other Sources of Variation