a or an before H?
Use an before a silent H: an heir, an hour, an honest politician, an honorary consul; use a before an aspirated H: a hero, a hotel, a historian, a historic. With abbreviations, be guided by pronunciation: eg an LSE student.
Do not include full stops between the letters of an acronym, including those in proper names: IMF, mph, eg, 4am, M&S, No 10, AN Wilson, WH Smith, etc. Where acronyms are spoken as a string of letters, use all capitals: BBC, CEO, UK, VAT. Where the acronym is pronounced as a word, write them as a word with an initial cap (such as Nato or Nasa), unless it can be considered to have entered the language as an everyday word, such as awol, laser, pin number and sim card. Note that pdf and plc are lowercase.
Use on French, German, Portuguese, Spanish and Irish Gaelic words (but not anglicised French words such as cafe, apart from exposé, lamé, résumé). People’s names, in whatever language, should also be given appropriate accents where known. Thus: “Arséne Wenger was on holiday in Bogotà with Rafa Benìtez”
is the preferred spelling, not ‘advisor’. But advisory with an ‘o’.
Always hyphenate the adjectival, whether it is eg seven-year-old child or 100-year-old coin. Hyphens should also be included in the noun eg ‘There are to be more school tests for eight-year-olds’ - though hyphens are not necessary in sentences such as ‘The missing boy is three years old.’

An age placed after a name should be sandwiched between commas eg ‘John Jones, 61, has been knighted.’
American spellings
Avoid the use of American English in general writing, except when referring to an organization’s name (eg Centers for Disease Control and Prevention).

A note about -ise vs -ize word endings: both forms are accepted in British English. All of the following spellings are acceptable in British English: finalize/finalise; organize/organise; realize/realise. It is more important that you use the same spelling in an entire piece than it is to choose -ise or -ize. Words ending in -yse always use an S in British English.

Source: Oxford Dictionary -ize, -yze, -ise, -yse
Do not use ampersands (&) in place of the word ‘and’ — only use ampersands in an organisation’s name, if the organisation does so itself (eg Marks & Spencer).
Any more
is the preferred version, not anymore.
indicate either possession (eg: the children’s nanny, the emperor’s new clothes, journalists’ pay) or the omission of one or more letters (eg: It’s a lovely day today; Life’s a bitch; Who’s been sleeping in my bed?)

There is no apostrophe in the possessive ‘its’ (eg: Virtue is its own reward).

Some common abbreviations do not require apostrophes (eg: phone, plane, flu).

Dates do not require apostrophes (eg: 1900s) - unless the century is omitted (eg: the England squad of ‘66).

Neither are apostrophes generally needed for plurals (eg: MPs, MBEs).

For names, use the possessive ’s whenever possible - eg: Burns’s, Jones’s, Charles’s, James’s, Dickens’s, Phillips’s. But be guided by how the last syllable of the name is pronounced - eg: Jesus’, Bridges’, Moses’, Hodges’, Griffiths’, Walters’ - also Wales’.

There should be an apostrophe before the word ‘time’ in sentences such as The game will be played in two weeks’ time or They stop work in one hour’s time.

The football ground in Newcastle is St James’ Park and in Exeter it is St James Park. The open space in London is St James’s Park (also St James’s Palace).

Queen’s College in Oxford has an apostrophe before the ‘s’. Queens’ College in Cambridge has it after.
If you want to use the term, our style is down under: ie two words, both lower case. Use Aus and Aussie if you must, but never Oz or Ozzie/Ozzy. New Zealand should be referred to only as New Zealand.