My son is 17 and often travels via DXB , he looks 18+ and hardly anyone would think he is still under 18. However in DXB they are on the ball and while he never has problems getting into any lounge he has ever visited including EK outstation lounges , he always gets denied in DXB. I reckon they have something on the computer now that alerts to age as they always request to see the passport. He was not happy when he got told to beat it when he had a 19 hour stop over ! haha
I believe the OP is departing LHR , you will not have a problem getting into the lounge in LHR if you are under 18. Secondly be very careful what you do and say in the UAE regarding trying to enter a location that serves alcohol it could easily open a huge can of worms for you and EK if something did happen.I think it was last year my son said they made a good point on why they can not let him in , the duty supervisor said if he fell over in the dining area or even in the shower and he broke something then a full internal investigation would happen and EK would be in huge trouble as it was a unaccompanied child involved , EK would lose their alcohol license and not to mention the possible legal actions and staff involved ramifications. My son did manage to get into the F lounge in concourse A once under a full escort after all staff had been informed no alcohol , a type of eat something and get out in under a hour type of deal. Interestingly to note the crew on his next flight were alerted to him being unaccompanied and he was told immediately without even asking or trying to take anything alcohol based that he will not be served anything with alcohol.
I would give it shot , who knows , i would be doubtful thou. Just act mature , calm and be polite and wear something adult would wear
, so leave the onesie at home ! Plenty of fast food joints in the concourse anyway if worse comes to worse.