Thanks Barry, Some recent CentOS-list emails have implied that if CentOS 5 is fully updated, it will be (effectively) CentOS 5.1, but this is clearly not the case! I've looked again at the Release Notes at http://wiki.centos.org/Manuals/ReleaseNotes/CentOS5.1 and see that CentOS 5.1 isn't relesed yet. So I'll have to be patient and wait - I hope that'll be rewarded when I find it does support my wireless card!
When CentOS 5.1 is released and you run yum update, all of the newer packages that comprise CentOS 5.1 will be downloaded and installed, which will upgrade you to CentOS 5.1. At which time, when you boot with the CentOS 5.1 kernel, you should see an 'eth1' device which will be your wireless nic.
Barry