I regularly use my Mac in the BA lounge normally the BT openzone. All I do is select it from the drop down for available Networks, open Firefox by default it opens the Openzone website put in my email address and then from memory select use internet or something from the next screen then surf as usual.
I have never had to alter anything or do anything complicated.
Although I have never been in GF only South or North it may be worth having a little trip in there to see if it is any better!