Hi UR,
Like you I'm pretty happy with the BT Yahoo Spam catching routine and like you I've found that you have to check it carefully. It isn't perfect, however, even after telling it three times that a certain e-mail isn't Spam, it still puts it in the Spam folder.
My Spam folder attracts 200-250 e-mails a day. I check it three times a day so the chore of going through the banal and ludicrous crap isn't too onerous.
One day it will change; until then we must just grin

and bear it.