bmi diamond club - What if

I have used my DC points to go to denver. GLA-PHL PHL-ORD ORD-DEN. what would happen if the flight from PHL - ORD is late and I miss the ORD-DEN flight? Would United look after me and get me on another flight? I believe they can't change bookings made by BMI. Is this correct? Would I need to call DC who would be closed by this time? If there was no award avaliability would I be stranded?

This is incorrect. They airline may pretend they can't or don't want but it is complete BS. At check in time (T-24 - T-72) the ticket comes under the control of the operating airline and they can change it.

Example, Air China didn't want to put me on another flight when my flight was delayed due to me being on a BD ticket. I fell sucker to it until another well travelled Chinese passenger over heard and told them off in Chinese for the nonsense. You should be treated like the operating airlines passengers after check in and don't settle for any lower treatment. In my flight all other business class passengers were being put on to other flights.