I don't find any proof it was banned, it just seems to have been a very unsuccessful TV drama made by Channel 5 (a small channel in the UK).
This article from 2003 talks about the poor viewer figures it got, despite a lot of press coverage at the time about how controversial it was:
Hear the Silence lost out to programming on all four terrestrial channels, including Channel 4's extreme science series, BodyShock, which continued to pull in viewers with a documentary about feral children.
Hugh Bonneville wasn't a big star until Downton Abbey. :)
PS. Did you know he's a Patron of "Medical Emergency Relief International" (http://en.wikipedia.org/wiki/Hugh_Bonneville)
Thy don't appear to be against vaccines (Vaccinated 202,036 children among other things: http://www.merlin.org.uk/what-we-do).