Credit rating agency Moody's has placed Santander UK's long term debt and deposit ratings under review following the announcement last week that its parent may be downgraded.
M&G tops both retail sales lists as investors seek out bond funds, while BlackRock's active and passive vehicles also prove popular.
The Financial Services Authority (FSA) has fined Santander £1.5m for failing to confirm to customers the circumstances under which its structured products would be covered by the Financial Services Compensation Scheme (FSCS).
Santander's offer to buy back junior debt from bondholders has drawn criticism from analysts who accused the Spanish bank of trying to lock in a profit at the expense of investors.
Santander, the eurozone's biggest bank, said a significant charge for mis-selling payment protection insurance(PPI) hit profits in Q3, but its capital cushion would lift it out of danger territory.
Spanish banking giant Santander has warned investors profits at the bank are likely to fall in 2012 and 2013 as the bank pumps millions into improving customer service levels.
HSBC's José Cuervo has joined Santander Asset Management as global head of Latin American equities.