Adding to Fratulent's previous post, and on the practical side of things..
If you decide to use the repeater solution, the setup could be as follows :
A high gain directional yagi antena for reception, located on top of the hill, a 35~ db masthead amp with at least a 110 dbm output to ensure that there is no overloading, feed that to a communal type of amplifier with a gain of 20~30 db and a 120 dbm (at least) output, this located as far possible down the hill (40~50m). The transmition aerial should be of a similar type but mouted for the opposite (vertical) transmition polorization.
Most communal type of amps have attenuators to adjust gain, so you can use them to ensure the setup does not go into oscillation.
All this offcoarse applies if all the chanels received are in one band (UHF), not being the the case AFAIK in Australia, unless things have changed sinse I was last down there (12 years ago).
The whole setup should not cost you over 350 $ for parts.
cheers