Gossip column jargon.
"uber-glamorous" = super glamorous
"roll-call of London's who's who" = everyone who is anyone [in the Daily Mail gossip columnist's view] was there
"a blaze of flashbulbs" = there were masses of photographers, all of whose cameras flashed as it was dark. If you think of one flashbulb going off, imagine what the effect is if 25 go off all at the same time - a veritable blaze of light.
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