Q: My iPad can't find my iPhone 4S via Bluetooth and vice verse, can you advise?

For what purpose are you trying to pair them?

You can only pair an iPad and iPhone for internet tethering (personal hotspot), and for certain peer-to-peer games and apps.

iOS: Understanding Personal Hotspot

http://support.apple.com/kb/HT4517

Use Bluetooth to tether your iPhone, iPod touch, or iPad

http://www.macworld.com/article/1159258/bluetooth_tethering.html

How to Connect an iPad to an iPhone Via Bluetooth Tethering

http://techtips.salon.com/connect-ipad-iphone-via-bluetooth-tethering-25472.html

Get a Mi-Fi http://en.wikipedia.org/wiki/MiF

 Cheers, Tom