UK Border Agency says:
Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Irish Republic, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, United Kingdom. Iceland, Liechtenstein and Norway are not members of the European Union (EU) but citizens of these countries have the same rights to enter, live in and work in the United Kingdom as EU citizens.
Swiss nationals are also permitted.
There are special rules for those from Bulgaria / Romainia.
There is also Youth Mobility Scheme (Tier 5) which enables those from Australia, Canada & New Zealand to work in the UK (subject to terms of the scheme - Youth Mobility Scheme)
So don't bother with the Brazilian.