NY -- Standard&Poor's CreditWire 1/15/1999 -- Standard&Poor's today lowered its long-term corporate credit, senior unsecured debt, and bank loan ratings on Marks&Spencer PLC and related entities to double-'A'-plus from triple-'A'. At the same time, Standard&Poor's affirmed its 'A-1'-plus short-term corporate credit rating and commercial paper ratings on Marks&Spencer. Standard&Poor's also affirmed its 'A-1'-plus rating on St. Michael's Finance PLC's commercial paper program, guaranteed by Marks&Spencer PLC. The outlook remains negative. The rating action reflects the company's announcement of much weaker-than-expected performance over the key Christmas period, as well as revised expectations for full year pretax profits. In its profit warning statement, Marks&Spencer has indicated