Collective nouns differ between British and American English. http://en.wikipedia.org/wiki/American_and_British_English_differences#Formal_and_notional_agreement
In BrE, collective nouns can take either singular (formal agreement) or plural (notional agreement) verb forms, according to whether the emphasis is on the body as a whole or on the individual members respectively; compare a committee was appointed with the committee were unable to agree. The term the Government always takes a plural verb in British civil service convention, perhaps to emphasise the principle of cabinet collective responsibility. Compare also the following lines of Elvis Costello's song "Oliver's Army": Oliver's Army are on their way / Oliver's Army is here to stay. Some of these nouns, for example staff, actually combine with plural verbs most of the time.
In AmE, collective nouns are usually singular in construction: the committee was unable to agree. AmE may use plural pronouns, however, in agreement with collective nouns: the team take their seats, rather than the team takes its seats. The rule of thumb is that a group acting as a unit is considered singular and a group of "individuals acting separately" is considered plural. However such a sentence would most likely be recast as the team members take their seats. Despite exceptions such as usage in The New York Times, the names of sports teams are usually treated as plurals even if the form of the name is singular.
The difference occurs for all nouns of multitude, both general terms such as team and company and proper nouns (for example where a place name is used to refer to a sports team). For instance,
BrE: The Clash are a well-known band; AmE: The Clash is a well-known band.
BrE: Spain are the champions; AmE: Spain is the champion.
Proper nouns that are plural in form take a plural verb in both AmE and BrE; for example, The Beatles are a well-known band; The Saints are the champions, with one major exception: largely for historical reasons, in American English, the United States is is almost universal.
That said, one person is never referred to as " a personnel " in either variant of the language. Personnel always are.
German collective nouns trip me up all the time (" information ", "a bread ", "a spectacles ") , but I soldier on using the English forms because the rest of the language is enough of a cruel joke to start with.