What's the time difference between Peru and GMT?

GMT -5 hours. 

Which countries combine well with Peru?

The Galápagos Islands, (flights from Lima connecting through Guayaquil, Ecuador).

What are the fiestas and cultural events in Peru?

Semana Santa (Easter): Many places throughout the country, Mar-Apr variable. Religious processions.
Inti Raymi, Cusco (24 Jun) Theatre and re-enactments of Inca history in the ruins of Sacsayhuamán, the temple fortress overlooking Cusco.

When's the best time to go to Peru?

The best time to visit the Andes is April to October, the dry season but at this time it is misty and chilly in Lima. The jungle is an all-year destination, as is Arequipa and the Colca Canyon.

What's the official language of Peru?

Spanish

What's the official currency of Peru?

Peruvian Nuevo Sol. Notes in local currency or US dollars can be withdrawn from the many ATMs using a UK credit or debit card. Numerous money exchange offices exchange US dollar cash (few accept euros or sterling and the rate may be poor).