Getting late here in IAD and my flyertalk seach skills are escaping me, so starting a new thread to ask this one:

I am a UA Gold. Was booked on a UA 016 ticket that IAD-BRU-ACC on UA and SN. Due to IRROPS in IAD, I was rebooked, still on a UA 016 ticket, IAD-LHR-ACC. The IAD-LHR is UA but the LHR-ACC is on BA. The layover is quite long in LHR, so wondering, will I be able to access the *A lounges in LHR even though my departing flight is non-*A? Thanks in advance!!