Wifi Issues (iPhone 5)

I have an iPhone 5 on Vodafone (UK) running iOS 6.0.2. My contract includes 3GB BT Wifi. My phone will not find BT Wifi despite full signal on Macbook pro in same room. New phone will connect to my home wifi but signal can be patchy and compared to my old iPhone 4 the signal seems weaker. I wonder is, this related to settings I can change, a software issue or faulty hardware. Any troubleshooting advice gratefully recieved.