Difficult question to answer; without doubt, the Beatles "opened the door." They were the first performers to have complete control over their recordings.
Thereafter, many of the artists were more niche.
The Who were initially regarded as leaders of the Mod culture, but the Small Faces were "more" Mod .
The Yardbirds, Clash, Sex Pistols, and the Specials all influential.
I'll include Bob Marley as he lived in the UK for a while.
Graham Nash ( ex. the vastly underrated Hollies,) formed Crosby, Stills, Nash and Young.