The compression and digitization software takes a while, as does the reconsttitution in your receiver. Transmitted info may be time-spread to handle interference and dropouts - see below.
XM Satellite Radio here in the colonies carries BBC World Service. The top of the hour beep comes out delayed about 14 seconds or so. XM accounts for at least 6 or 8 seconds since they transmit redundant data which carries the signal through dropouts of as much as 3 seconds such as when one drives under a bridge. One's receiver patches it all back together. There's a lot of digital magic in the receiver. One suspects that also applies to the digital services in the UK.