For your information, the current UK plug (three pins of rectangular cross section) is uniquely British design and has only been adopted by very few countries, all of them ex-colonies or similarly connected to Britain. Some countries do not have a uniform standard and you will come across a variety within there and then very, very occasionally a UK style socket among those). Not all former UK possessions have adopted the UK plug design, far from it, and therefore worldwide you are much more likely to require an adaptor than not. The European style two pin is the design you will come across most often worldwide and, apart from the UK, the most notable countries where a different design from that two pin design does not dominate are Australia, Japan and the USA. Within the European two pin design there are several variants, this in spite of efforts to unify the standard throughout Europe and beyond.