Zeppelin were never "mega" in the UK. I know, I was there. The most popular bands at that time were Pink Floyd, T Rex and ABBA who outsold Led Zeppelin big time in England. By 1976 Zeppelin were considered "old farts", the last of their fans congregating for the Knebworth shows. The musical climate had changed so much they never played one concert in the UK for the 1980 Tour, straight to Europe with their collective tail between their legs.
In the 80's they were all but forgotten, considered "old fashioned" and "bloated dinosaurs." It's only since the late nineties that they have been re-evaluated and found worthy by the almighty music critics and media.