If you are looking for lines that contain both strings Banner
and SSH-2.0-OpenSSH_4.3p2 Debian-5ubuntu1
then you can also use grep and cut.
Grep version with cut
nmap-banners -sV -vvvvv localhost|
grep 'Banner.*SSH-2.0-OpenSSH_4.3p2 Debian-5ubuntu1'|
cut -d" " -f3|
cut -d":" -f1