Britpop was a British cultural movement from 1993 onwards (it was a term coined by the music press and much debated which release spearheaded it; with Suede's debut album or Blur's "Popscene" single). It grew out of the indie and Madchester scenes of the previous decade and was heavily influenced by the British rock bands of the 1960s: in particular The Beatles, The Kinks, The Who, and The Small Faces. It was seen as a backlash against American styles, most particularly Grunge. Heavily melodic, with a traditional bass / guitar / drums / keyboard lineup, Oasis and Blur took the style around the world with much success. It was, as a style, essentially finished by 2000.
Britpop should not be applied to bands / acts from the sixties or outside this defined 1993 to 2000 era. Just because a band is British, or British and recorded in this era, that does not make them Britpop. Use carefully.