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Only more cost effective if you already have a netbook lying around.
"I'm using a 10"Asus which cost £30 on ebay."
You are sort of correct about needing Enterprise or Ultimate versions of Win7. Usually the virtual wireless adapter cannot be created or a hosted network cannot be started in Windows 7 Home Basic or Home Premium. There is a pretty well known workaround invoked using an Administrator command prompt.
Something like "netsh wlan set hostednetwork mode=allow ssid=myAP key=12345678" to create a virtual wireless adapter. The SSID will be called myAP with the password 12345678 for virtual AP.
I tried that without success but that might just be me.