Let's assume and hope that you just purchased one ticket, they know your final destination but if you are to pickup your suitcase and you don't, it will remain in Baggage Claim.
What you can try doing (Dont know if OA does that) is for them to tag your luggage LHR and send it through. I think they would have to contact UA but afterall they do have both a ticketing AND you "may check baggage to" BA
Good luck, have a safe way home