Turned out to be a couple of very basic problems, but it didn't end there!
The desktop which was manually assigned an IP address, but wouldn't connect to the internet was solved by entering the router IP address as the DNS server - forgot to do that!
The laptop with internet access but would not appear on the LAN turned out to be a problem with it's own firewall (Zone Alarm). Doesn't matter how I configure Zone Alarm, the only way to get it to access the LAN is if I disable it completely. I'll have to rely on Windows Firewall and the one in the router.
Have encountered more problems with WPA encryption causing the connection to fail after about 60 seconds - eventually had to resort to using WEP encryption.
Also having problems with the laptop on boot-up. The wireless software hangs at every boot, although it does still operate. EZ Connect ? I don't think so SMC!