Why not let him just use them anyway Clare? He afterall doesn´t actually have to buy anything and will at least get to see more properties. That is again what you lot always suggest anyway, see as many as you can before making a decision, that way you are better informed. If he was to see properties with all the big REA´s as well as small ones doesn´t that give him a stronger position to work from?
Excluding big agents just means less properties to see, unless you are fluent spanish and can ring vendors direct via newspapers, something which not a lot of people enjoy the privilege of.