According to its Ministry of Foreign Affairs, all visitors to Luxembourg should be able to provide relevant documents at the border relating to the purpose of their visit and proof of sufficient means of subsistence for their stay.
British passport holders and other EU citizens do not require visas to enter Luxembourg for a period of up to three months. Passports should be valid for at least six months. US citizens can also enter without a visa for a period of up to three months.
Luxembourg Embassy in the UK
27 Wilton Crescent
Tel +44 (0)207 235 6961