BA will always give priority to the their staff, getting upgraded from World Traveller to either Traveller Plus and Club is very slim as mentioned, if you know the A4's and A6's (Senior Staff or Supervisory Staff ).
I got upgraded to JFK to Club but could not have the club meal.
I find the staff at JFK T7 very unhelpful and rude. You will get a better chance of upgrade from MAN, LGW than LHR.
All you can do is ask politely at the check in desk to put a "SFU" Comment.
Good luck