I have a flight tomorrow to middle east through BMI from Heathrow terminal 1 and want to ask few Qs:?

I have checked-in online and got e-boarding p. Now i have to drop my hold luggage using the drop luggage counter. I want to know how does it work? will it be flexible to allow a few kgs above the allocated free allowance? and would i be able to get the hand carry tags from there aswell?