Nadia Sawalha is a very well-known British actress and TV presenter in her own right. She's one of the regulars on Loose Women, a long-running daytime talk show.
https://en.wikipedia.org/wiki/Loose_Women
The movie got heavily edited from Joss Whedon's original script to make it more comedic. When it came to the TV series, that script would be used as Buffy's backstory as to why she moved to Sunnydale in the first place.
Based on the Craig Thomas novel; it's arguably the first techno-thriller and a pretty good read in its own right. There's a book sequel called Firefox Down as well. Both are now available in new editions after years out of print.
The "earthquake bomb" was a real thing, but I don't think Mosquitos carried them.
https://en.wikipedia.org/wiki/Tallboy_(bomb)
https://en.wikipedia.org/wiki/Grand_Slam_(bomb)
When Little Boy was detonated at Hiroshima, Truman used the Grand Slam as the comparison to demonstrate its power.
He was great in Doctor Who as well - he appeared in the Dreamland animated series as the main villain, guested as a Western-music loving Soviet scientist in the excellent "Cold War" and played an "Unbound" Doctor for Big Finish.
Rest in Peace.