I went into MAPLIN's today and tried to buy a 17C42(A)/43/44, but was told
that it was discontinued,

 the only 17CXXX part they list is a 17C75X in a 'square' package
(PLCC,CERQUAD,TQFP or somesuch).

Is this just a MAPLIN quirk or do they know something we don't?

TTFN Paul