I have a flight booked to moscow in First and im connecting same day to a cathay flight to DPS via HKG i will have around 50kg luggage and was hoping ba can check my bags thru to hkg but just noticed that my cathy biz ticket only permits 30kg will BA be able to check thru as its on a dif booking ref! and also will ba be able to take payment for excess

Also do i neeed a transit visa for Moscow ?

Thanks