Are you a boarding cattery doing abit of rescue or entirely rescue? If you are a rescue are you on cat chat? They offer free homing pages and have a top cat section that does help get those harder to home cats into new families
www.catchat.orgHave you looked into getting stable homes for them? Make sure the people will feed the cats daily and provide all other necessities.
Sadly many people dont want to put any effort into winning a cat round, personally i like the timid ones
Iv had Simon comming up to 3 years and he jumped on the bed with me for the first time a few nights ago and stayed there all night. He was a timid little feral who was caught at 5months of age