Interesting. I just went to the lounge, showed my SE card, told them I had just spent 10 hrs on an AI jumpseat and asked if I could use the showers. The girl said "sure" and set everything up for me. I only got the idea from the girls at the LHR MLL who had told me on my last trip (on a revenue ticket for the record!) that the Arrivals Lounge would accept SE's regardless of carrier flown.

I personally haven't nonrevved on AC for well over 10 years (and have long outgrown my own interline priviledges on AC metal anyway) so I don't claim to know how their system works right now. I also agree that nonrevs shouldn't try to weasel things they aren't entitled to, which is why I like to ask politely to figure out what I am entitled to.