Used to do this interchange until BA down-graded CE seat pitch. Now we fly Turkish, much much better - check baggage right through, of course, and decent seat and food.
You have to wait to pick up your luggage in the Domestic Terminal, walk a good ten, maybe fifteen minutes to the BA check-in at the far side of the International Terminal (more if you have to use a trolley, as the lifts to take you up one floor in Domestic are hair-tearingly slow). The time it takes to get through immigration is a lottery depending on time of day, etc, and you only check in your electronics at the gate (or better still have them packed in your hold baggage already). I seriously doubt you'd do it in 75 min.