MADRID (Reuters) -Spain's Santander on Tuesday said its third-quarter net profit rose 12% year-on-year following a solid performance at its main retail business and lower loan loss provisions.

The euro zone third-biggest lender in terms of market value booked a record quarterly net profit of 3.25 billion euros ($3.5 billion), slightly above the 3.1 billion euros expected by analysts in a Reuters poll.

Results are expected to be somewhat overshadowed by Santander's UK unit postponing the publication of its own results following a London court ruling last week that found that motor finance brokers must fully inform customers about commissions when taking out car loans.

Santander UK, which is one of a number of key providers of motor finance in Britain, said it was "not practicable to reliably estimate at this point in time the extent of any potential financial impact" and that it was taking time to assess it.

Santander however published the results of its British unit as part of the earnings group. A spokesperson for Santander said on Monday the bank did not expect any material impact from a review by the Financial Conduct Authority related to the London court decision on motor finance.

($1 = 0.9251 euros)

(Reporting by Jesús Aguado, editing by Inti Landauro)