If MAC filtering had been in place, I don't think you would have 'connected'. (also if they have a wireless network with no encryption, I would be surprised if they had MAC filtering.
I would have looked at the 'Support' tab on the wireless connection status screen. This shows whether a valid DHCP address has been assigned. You could then try pinging the default gateway (wireless router) and possibly tracert to a well known address (
www.bbc.co.uk).