I have sampled the BA, *G (I think it was LH or LX), KL and EK lounges at DXB. Even during peak hours, I found DXB by far the nicest. I am lucky in that I usually avoid the peak flying times but even when I land around 6am I can usually find a single seat. To the OP: you should be able to take a guest in without a problem. You can try the main lounge [some people have had success during off peak hours] but my guess is that you are arriving off EK 040 at 00:15 - in this case just head straight to the other lounge.

Cheers,