So, how does IB get out of IAG? Certainly not of it's own violition. IB is owned by IAG so can not simply withdraw it's supposed membership in a huff.
And what exactly has gone to the Brits? It seems that because WW is CEO of IAG, the business is viewed as solely British. Go take alook at the IAG wbsite and look at the Board of Directors, the Senior Management and so on.
Then re-read your post and consider again your comments.
Finally, how long do you think an IB business in it's current format and losing so much money would survive on it's own? Again, go look at some stats on business performance in Spain, unemployment figures and outlook forecasts.