Final answer:
John and Charles Wesley's headquarters in London was known as the Foundry, and their religious conversion was significantly influenced by Martin Luther's writings on Justification by Faith.
Step-by-step explanation:
The location of Wesley's headquarters in London for many years after John Wesley's return from the colonies was the famous Methodist center known as the Foundry, which served as the base for Wesley’s ministry. John and Charles Wesley were Anglicans who experienced a significant religious conversion which was greatly influenced by their encounter with the Moravians and the writings of Martin Luther, especially his concept of Justification by Faith.
Their practice of methodical religious devotion led them to be called Methodists, which later became the name of the Protestant denomination they founded. John Wesley's conversion occurred in 1738, shortly after Charles Wesley's, marking the beginning of their fervent missionary and public service work that had an immense impact on both England and the American colonies.