Iirc they were actually props built for Loony Tunes: Back In Action, hence their stellar condition and slight inaccuracies to the originals.
Most of the old Dalek props from the 60s movies were already repurposed into props for the show, and by the end of the series the Daleks from both the show and movies were in... well "rough shape" would be putting it mildly, they were basically falling apart given how fucking cheap the BBC was.
They almost never replaced them, instead just taking them apart, patching them up and re-painting them over and over for several decades.