Language
Pronunciation
The S&P pronunciation of the Hebrew alphabet and vowels is generally in line with the Sephardi pronunciation used in modern Israel, with the following exceptions:
Bet/Vet: The S&P - like a number of other Sephardi communities - traditionally make no distinction between Bet with and without a dagesh, pronouncing both "Bet".
Note: I am not sure if this quirk is historically or linguistically related to the well known Spanish habit of pronouncing B and V the same - in fact I am inclined to think that it is not - but it may be worthy of note that that habit goes back a very long way. As early as the first century BCE, the Roman poet Quinto Horacio Flaco quipped of Latin speakers from Spain: "Beati Hispani quibus bibere vivere est!" ("Those happy Spaniards, for whom 'to live' is [pronounced the same as] 'to drink'!").
Ngayin: The most distinctive S&P letter is Ngayin. Apparently unable to pronounce a genuinely guttural sound like their eastern cousins (and unwilling to effectively ignore it like the Ashkenazim), they transliterated - and actually pronounced - the "Ayin" as "ng". So - for example - "Ba'avoor Daveed Avdecha" is transliterated in the choir's music books as "Ban-ga-boor Daveed N-gabdecha" (a source of endless amusement to younger members of the choir).
However, due to the influence of modern Ivrit, as well as the dilution of the S&P with Sephardim from other lands, both these peculiarities are today largely ignored by lay members of the kahal, and even some of the ministers. What remains unequivocally is a determination that the Ayin be pronounced - whether as "ng" or gutterally - but not ignored or treated as an "Aleph" as it is by many Ashkenazim.
Aleph/Heh, Sin/Shin, Tzaddik: Although these letters are today pronounced the conventional way, mention should be made of some peculiarites in the transliteration of congregational terms containing them, indicating that two or three centuries ago they were pronounced differently (possibly due to English usage current at the time).
Sha'ar Hashamayim, the name of the kahal, is referred to in ancient documents as "Sa'ar Asamayim"
Etz Hayim, the society dealing with communal Torah publications is officially known as "Heshaim" - presumably this word was originally pronounces "Hes-Haim", but nowadays most people [except me] pronounce the "sh" as in "Shabbat"
Haskamot, the rules of membership of the kahal, are officially termed "Askamot"
Hechal, the ark, is even today called the "Echal"
Vowels: In common with most Sephardim - and unlike Ashkenazi and modern Hebrew pronunciation - all S&P vowels are pronounced as pure vowels and not dipthongs. So Segol and Sere are both pronounced like the E in "let" not as in "they". Holem is pronounced like the O in "lot", not as OY, OWE, OW, or EY.
Enunciation
S&P enunciation is traditionally meticulous. The difference between the silent and vocal Sheva is studiously observed. Furthermore, the difference between "milra" (accent on last syllable) and "mil'el" (accent on penultimate syllable) is strictly observed (with only very few exceptions), even when fitting words to a melody. This is unlike the Moroccan or Ashkenazi customs, which routinely mis-enunciate when doing this.
I consider the following MP3 recording an exemplary piece of a well-enunciated London S&P chanting (from the Shabbat service, by my friend Prof. Daniel Jackson):
Aramaic Pronunciation
1) Kaddish
Unique - I believe - to the S&P is their traditional pronunciation of three Aramaic words that occur in Kaddish:
Kal instead of Kol
Be-ngalma (occurs twice) with the accent on the second-last syllable (mil'el) instead of the last syllable as it wou;d be in Hebrew
Ba-ngagala with the accent on the second-last syllable (mil'el) instead of the last syllable
One explanation may be that the S&P actually have a tradition that this is the correct way to pronounce these Aramaic words; but another may be that they simply invented it as a way of distinguishing them from Hebrew words that have different meanings but otherwise sound identical.
Yitgadal veyitkadash shemeh rabah.
(Congregation: Amen)
Be-NGAL-mah divera khiruteh, veyamlikh malkhuteh,
Veyatzmakh purkaneh vikarev meshikheh.
(Congregation: Amen)
Behayekhon uvyomekhon uvhaye dekhol Bet Yisrael,
Ba-nga-GA-la uvizman kariv ve-imru Amen.
(Congregation: Amen. Yehe shemeh rabah mevarakh, le'alam ule-almey almaya yitbarakh.)
Yehe shemeh rabah mevarakh, le'alam ule-almey almaya yitbarakh.
Veyishtabakh veyitpa-ar veyitromam veyitnaseh
Veyit-hadar veyit-aleh veyit-hallal, shemeh dekudeshah berikh hu.
(Congregation: Amen)
Le-elha min KAL birkhata, shirata, tishbekhata venehemata,
Da-amiran be-NGAL-mah ve-imru Amen.
(Congregation: Amen)
2) Kal Nidrey and Kal Hamira
Both in the opening word of Kal Nidrey on the Eve of Kippur, and in the annulment of leaven (Kal Hamira) on the Eve of Passover, the word for "all" is written without a makaf connecting it to the following word, and therefore pronounced "Kal" rather than "Kol". This seems to be an S&P usage that applies to all appearances of this word in Aramaic rather than Hebrew contexts.
Use of Portuguese
In common with most S&P communities, the native language of the original members was Portuguese. Hence the announcement of the mitvot (who is to open the ark, carry the sefer, etc.) has always been made in that language.
Although it is unlikely that more than a handful of today's congregants speak so much as a single word of Portuguese, the custom remains. Fortunately many of the words are similar enough to English to be vaguely comprehensible, and the effect is of course delightfully quaint and ethnic.
Use of Spanish
The only Spanish traditionally included in the services is a translation of the Haftara on the Fast of Av.
However, in recent years a Spanish table hymn - Bendigamos - has been introduced to the London community from New York, being sung immediately before or after Birkat Hamazon. Although not an authentic London custom, it's been adopted as a sort of club song. It originates from a Spanish-speaking S&P community in Bordeaux that was destroyed by the Nazis.
You can read more about it on the Bendigamos page of the London Sephardi Music site.
Use of Ladino
Ladino is not used by the S&P of London.
Use of English
English is used only for congregational announcements at the end of the service, and for the last fifty years at least has followed a simple and charmingly stilted formula, something like this:
The congregation is cordially invited to Kiddush in the Montefiore Hall shortly after the service.
This evening mincha will be read at a quarter before six o'clock, to be followed by Arbit.
Weekday evening services will be held in this synagogue at 7 o'clock.
On Friday next the afternoon service will commence at a half after six o'clock.