The new 2015 series, which will feature CG characters on live-action miniature sets, has its Lady Penelope in Pike, most recently seen in The World's End. Even better news for longtime fans, though, is that David Graham will reprise his role as her chauffeur, Parker.
The rest of the cast are not as familiar:
Unstoppable inventor Brains will be voiced by Kayvan Novak (Fonejacker, Facejacker) whilst Tracy brothers Gordon and John are both played by Thomas Brodie-Sangster (Love Actually, Game of Thrones). Rasmus Hardiker (Saxondale, Lead Balloon) has been cast as both the youngest and oldest Tracy brothers Alan and Scott. The fifth Tracy brother, Virgil, will be played by David Menkin.
Tracy Island matriarch Grandma Tracy is voiced by Sandra Dickinson (Amazing World of Gumball, The Hitchhiker's Guide to the Galaxy) and master villain The Hood played by Andres Williams (M.I. High, Foyle's War).
Plus Thunderbirds Are Go! will feature new characters including Kayo, the Tracy brothers' friend and fellow island resident, who will be played by Angel Coulby (Merlin, Dancing on the Edge) and Colonel Casey voiced by Adjoa Andoh (Invictus, Doctor Who)
I'm still really not sure the retro aesthetic of Thunderbirds can work particularly well today, but it sounds like they're trying their best. Then again, hiring original voice actors doesn't always mean fealty to source, as Peter Cullen could probably attest.