UK prisons strictly segregate sex offenders from other inmates. They have their own wing, and even on Visits they sit in completely separated areas.
There are at least eight prisons here which are solely for sex offenders. (for example, HM Prison Bure, on the site of the old RAF airfield at Coltishall, Norfolk with over 500 inmates.)
And while they're locked in there they aren't harming or ruining the lives of children.