The scenario you raise with the satalite dish is an interesting one. One of the ammendments to the 10142 electrical regs had the requirement that every installation have an earth terminal specifically for use by other contractors and installed in such a way that allows access without entry into the DB. If the electrical installation is certified up to or beyond the date when amdt6 was introduced then I'd say the TV installer can install the earth because the earth terminal that's remote from the DB accomodates this.

6.11.5 A readily accessible earthing terminal shall be provided for the
bonding of other services such as a telephone, an audio system, a video, and
the like, to a building. Such an earthing terminal shall be bonded to the
consumer’s earth terminal by a conductor of at least 6 mm2 copper or
equivalent, and shall be identified by the earth symbol (Amdt 6)
NOTE Providers of services other than the electrical power services should not access
the distribution board or other parts of the electrical installation.

If a TV installer fits a satalite dish then runs and terminates a suitable earth wire from the earth terminal that's specifically provided for him as per amdt6, he wouldn't be expected to have the test equipment or competence to run impedance tests on this earth and wouldn't be able to issue a certificate of compliance for this addition/alteration to the electrical installation. The million dollar question would be is the owner of the installation then be required to get an electrician in just to certify this earth? The only answer I can give at the moment is there's valid arguments in both directions. I'm going to think about it for a while and probably do some reading of the regs and definitions before I jump in with an opinion.