vs251 23/5 - connecting to BMI GLA

Hello - I am flying back PE tomorrow from Shanghai and have to then transit to Glasgow. Question I have is the arrival time means no Revivals lounge available at LHR - will I be able to use BMI lounge at Terminal 1? I know they are codesharing some flights now but from reading I think I may only use BMI lounges if the flight is international. If anyone can tell me how busy the flight is tomorrow that will also be welcomed I may try and use miles to upgrade evn though booked on K!