When Daniel Jones in 1949 produced the seventh edition of his Outline of English Phonetics he felt obliged to qualify the statement (at §755) that "In non-dialectal Southern English ... no r-sound is ever used finally or before a consonant' by adding the "except occasionally when ə is elided." A few lines further on he mentioned that 'Exceptionally r occurs before n and l in one pronunciation of words like barren and quarrel ...' – which he considered to be 'more usually' heard with an /ә/. The two forms of these two types of words had always until 1997 been conveyed in the EPD (Daniel Jones's English Pronouncing Dictionary) by representing the schwa in italic type, as is still the case in the Wells LPD. In 1997 Roach substituted a superscript non-italic schwa for the previous notation. The ODP uses a non-italic n with subscript syllabicity mark. By contrast with his Outline comment Jones's explanation of the indication of italicised letters was that the items were to be taken as of 'approximately equal frequency'. They are nowadays probably at least as usual in the unelided forms and the Gimson 1977 less mathematically precise re-wording of the EPD text (p. xxiv) to 'commonly omitted' was to be welcomed.
In the face of some EFL learners' tendency to dwell unsuitably on /ә/ sounds, which are often very short, they can at times be the safer target pronunciations for the learner of (British etc) English as an additional language. This was an important factor in their adoption as preferred recommendations of many words in my 1972 Concise Pronouncing Dictionary of British and American English. It may well be that General British usage is drawing slightly away from General American in this respect and that in GA the more leisurely rhythm predominates.
In its slightly less extensive (though of course then much more up-to-date) description of the British English segmental phonemes, Gimson's Introduction to the Pronunciation of English of 1970 chose to skim over this topic with the brief generalisation 'RP /r/ occurs only before a vowel'. However, the fact was and no less still is that it is very characteristic of contemporary General British pronunciation to elide /ә/ from the unstressed sequence /r/-plus-schwa-plus-consonant quite often even in lexical pronunciations and very often indeed in syllables in proclitic or enclitic prosodic situations, ie in weak syllables either side of accented ones.
The examples given below are typical of such elisions. They are arranged according to the consonants involved (in the order voiceless, voiced, nasal and approximant). Many of them witness the fact that mere phonemic analysis — invaluable though it may be as a pedagogical device — has many inadequacies. The problem is that, although for many speakers these forms could be said to be more usual than the unelided variants, the elisions are in some situations very unusual for most words (except the /-rn/ and /-rl/ types) in connection with such stretching prosodies as the rising-falling type of tone. This no doubt supports the general opinion that their underlying phonological forms are plus schwa rather than minus. However, there is no longer to be any doubt that for very large numbers of GB speakers the now elided forms have replaced as regular surface ones the previous values suggested by their spellings. It is rather interesting to note that phonological history is repeating itself in that many non-demotic British speakers can be heard currently to elide – certainly in relatively negligent articulation – these newly pre-consonantal r's as in eg /vei naɪs/ for very nice and /teәbli sɒi/ for terribly sorry.
/jʊәr`pɪәn/ European, /`ʧɪrpɪŋ/ chirruping. No doubt this new form came about after chirping had become less onomatopoeic in losing its /r/.
/ɔ`θɒrti/ authority, /`ʧӕrti / charity, /km`pærtɪv/ comparative.
/ɪ`lektrkl/ electrical. Occurring between two voiceless consonants the /r/ is syllabic and devoiced.
/`mɪrkl/ miracle, /ə`merkən/ American, /`kӕrkəʧʊə/ caricature, /ˋværkəs/ varicose.
/`lɪtrʧə/ literature, /`temprʧə/ temperature. The /r/ is devoiced in both.
/`glɔ:rfaɪd/ glorified, /̩pjʊərfɪ`keɪʃn/ purification.
/ӕrθ`metɪkl/ arithmetical, /`mӕrθən/ marathon.
/kɒr`spɒndənt/ correspondent, /ɪm`bærsɪŋ/ embarrassing, /`faɪr skeɪp/ fire escape.
/`flʌrʃɪŋ/ flourishing, /`pærʃuːt/ parachute, /`perʃɪŋ/ perishing.
/`eɪbrhæm/ Abraham, /`ɒpr haʊs/ opera house. In this last item the /r/ may be devoiced.
/`ærbɪk/ Arabic, /`hɒrbl/ horrible.
/`merdɪθ/ Meredith, /`pærdaɪs/ paradise, /`pærdi/ parody.
/`ærgǝnt/ arrogant, /ɪr`geɪʃn/ irrigation.
/ɪn`kʌrʤɪŋ/ encouraging, /ɪn`kɒrʤəbl/ incorrigible.
/der`veɪʃn/ derivation, /ðeər v biːn/ there have been...
/ɔːr ðeɪ/ ...or are they... /ˈweər ðəʊz/ Where are those...
/əz ˈfɑːr z aɪ/ As far as I... /hɒr`zɒntl/ horizontal.
/`kӕrml/ caramel/, /`heərm/ harem / `ʤermi/ Jeremy /`θɪərm/ theorem. The word-final but not necessarily the internal /m/s in such words are syllabic.
/eər`nɔːtɪkl/aeronautical; cf /eərn`ɔːtɪkl/ in which the /n/ is possibly syllabic, as also with /`aɪrni/ irony, /`baɪrn/ Byron, /`ɒrnʤɪz/ oranges. /`ӕrndl/ Arundel. /kɒr`neɪʃn/coronation.
/ɪn`ʃɔːrns/ insurance, /`peərnt/ parent. Reductions to un-syllabic /n/ are the less common versions tho not certainly so in the case of /`fɒrnə/ foreigner.
/paʊər ŋ `glɔːri/ power and glory
/`bærl/ barrel /`kwɒrl/ quarrel, /`hærld/ Harold, /ðeər l/ there'll ...
/`febrri/ February. This occurs with one or in isolation with two syllabic /r/s.
/`terrɪst/ terrorist. In running speech this may lose the single syllabic /r/ it usually has in isolate use – making it homophonous with terraced.
/ðər r ə/ There are a... /`laɪbrri/ library. No doubt as an over-reacting procedure of avoidance of the purist-disapproved but very common non-demotic un-syllabic-/r/ version /`laɪbri/, there exists an occasional hyper-corrected version of this word giving it three /r/s as /`laɪbrərəri/ suggesting that the speaker takes it to be spelt "librarary"!
/`kærjɪŋ/ carrying, /`gærjələs/ garrulous, /`sɪərjəs/ serious /`wʌrjɪŋ/ worrying
/`bɒrwɪŋ/ borrowing, /`kærweɪ siːd/ carraway seed, /`fɑː r weɪ/ far away
Eustace, S.S. (1965). The assimilation of /ə/ in present English. Proceedings of the Fifth International Congress of Phonetic Sciences.
Gimson, A. C. (1970). An Introduction to the Pronunciation of English. London: Edward Arnold.
Gimson's Pronunciation of English (1994, 2008, 2014) recast by Alan Cruttenden. London: Edward Arnold.
Jones, Daniel (1918, 1932, 1949 etc) An Outline of English Phonetics. Leipzig: Teubner / London: Cambridge University Press.
Jones, Daniel (1956). English Pronouncing Dictionary. Eleventh edition. London: J. M. Dent
Jones, D. (1997, 2006, 2011) Editors: P. Roach, J. Hartman & J. Setter. English Pronouncing Dictionary. Cambridge UK: Cambridge University Press.
Upton, Clive, Wm A. Kretzschmar Jr & Rafal Konopka (2001) The Oxford Dictionary of Pronunciation for Current English. Oxford: OUP. ("ODP")
Wells, J. C. (1990, 2000, 2008) Longman Pronunciation Dictionary. London: Longman Group UK Limited (“LPD”)
Windsor Lewis, J. (1972, 1979) A Concise Pronouncing Dictionary of British and American English. London: OUP.