Do you have Virgin Media's "SuperHub" router? On the back there's a panel titled 'Your Wireless Settings (default)'
SSID: virginmedia1234567
Passphrase: abcdefg
SSID is the name of your wireless network, passphrase is the password to connect. On your iPad go to Settings > WiFi and select your network from the list, put your passphrase in the password box when requested, and that should get you straight in and online.
Just out of interest do you have another computer successfully connected to your Virgin Media wifi? If so, then the fault will probably lie with the iPad connection, rather than the router.
If your iPad doesn't see your wifi network, try rebooting your router. Still can't connect? Try a hard reset on your iPad - press and hold the home and power buttons together, then release them when the Apple logo appears on screen and let it start up as usual.
If you still can't connect, then restore the router to the factory defaults and try again. If your wifi isn't working at all, you'll need to connect to the router by ethernet, then in a browser, go to
http://192.168.0.1 - this is the default address for the VirginMedia SuperHub, but may be different if you have another device - it's usually written on the back panel, along with the login details for the device. Again, assuming it's a SuperHub we're dealing with, the defaults are username "admin" and password "changeme"- you'll be prompted to change the password, at least - and you should.
From there you should be able to navigate to the Super Hub Settings page, scroll down and select 'restore factory defaults'. Let it reboot, and try again. If there's still no joy, and you don't have any other devices connected over wifi, then I'd suggest calling virgin media to check the router.
HTH Pete