Tight slot
Provided the itinerary is on a single 'ticket' the bags should be through-checked regardless of the fare components.
Under MITA the participants agree who is responsible for dealing with the passenger in the event of a problem, and how the liability is shared. This requires that the passenger is holding one ticket (one contract).
With two or more tickets the liability issues are different and some airlines, including BD, will refuse to through-check bags on journeys involving more than one ticket.
Globespanfan
What you describe appears to be a single ticket but you might want to double check. Does your confirmation include the e-ticket number(s)? If you have only one number beginning with 236 then that is a BD ticket. It could be an American Airlines ticket - beginning with 001. If you have two ticket numbers with 236 and 001 prefixes then it is doubtful in BD will check the bag through.
If you don't have the e-ticket number, check with Opodo and ask them if you have one or more tickets.
When you check in have a look at the airport code on the baggage tag that the agent attaches. It should be MCO. If it is LHR, then your bag is only going to Heathrow.