Hello Tina
Welcome to Rabbit Rehome.
I am not too sure how to reply about the question you pose, each individual rescue or person who has a rabbit looking for a home normally adds their rabbits to the rabbit rehome website and to this forum. Although it is a nice offer Adele and Tamsin I am sure won't have the time required to add all the rabbits on these sites to you forum. It is an area which only individual rescues can do as information does require to be kept up to date if websites are to be kept up todate.
As a person who is involved with the rehoming of animals who belong to a rescue, I have to admit that many do not advertise their animals on sites which breeders use as their are many differing values and ideas between the two areas this can present problems. As you may appreciate this is a very emotive topic which frequently gets discussed at varying times on the forum. The idea is very good and potentially helpful to those who are looking to find / rehome an animal
Janice
I run a sanctuary and i am glad that there are many people who also help rabbits out there.