who pays/selects an independent valuer ?

Just a thought---does anyone know how this type of arrangement happens?How "independent" can a valuer be---if he gets a phone call from one of the two parties involved ?Do the two parties pool some money and someone else chooses? If this is the case---how does HE know that he is not accidently playing into one of the companies best mates valuation business's?
Any thoughts would be appreciated---and i might ring Altona tomorrow and ask them---if i get a constructive answer,i will post it tomorrow.