That seems to be “eccentric” not “eccentricity” (your failure to cite the source of the quoted definition makes it harder to tell, but it is almost verbatim the M-W definition of “eccentric”.)

(Eccentricity, the noun used, is just fine with “the British” if onenis referring to the collective manner in which they are eccentric, the plural “eccentricities” would be appropriate if one was referring to the diversity of particular manners in which they were eccentric.)