Its importance has grown in recent years after the banking crisis forced two of the U.K.'s largest financial institutions, Lloyds Banking Group PLC and Royal Bank of Scotland Group PLC, to halt dividend payments after the government bailed them out.

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HSBC, the most active underwriter of "dim sum" bonds overall, and Royal Bank of Scotland Group PLC, for instance, have formed teams dedicated to developing their offshore yuan services in London.

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"You're seeing a gradual recovery in consumer spending from some of the disastrous numbers we saw after the crisis in 2008, " said Omair Sharif, an economist at Royal Bank of Scotland Group PLC in Stamford, Conn.

WSJ: Consumers Step Up Spending