British Airways complaint: Lost Luggage

We boarded a plane from Manchester to Heathrow and then travelling from Heathrow to Japan. British Airways did not load our luggage on the plane at Manchester. We are travelling with an 8 month old baby and only have the clothes we are wearing. We filed the necessary forms and followed that up with phone calls. In the first phone call they said they would put in an urgent request to put our luggage on the next plane (that didnt happen) the next phone call we are told there is nothing they can do.
Their tracking site shows that they are still trying to locate our luggage 36 hours after the event. We know that our luggage is still in Manchester as we have an airtag in one of the suitcases. We have arrived in Japan its 3 degrees with a baby thats not got any of her requirements or clothing and we have just the clothes on our back.
We saved hard for this holiday and now do not know how to proceed with this problem