Do not resign!
First I would like to express my deepest sympathy for the pilots here that resigned from current job after getting a contract and a start date with BA.
I have had the great joy to listen to probably 100s of FOs being on the way out of my outfit for greener grass.
It always strike me as odd how obsessed they are with " honoring" the present contract with regards to notice.
In bad times as we have had lately,there is no points for being a Gentleman. It is survival, for individuals and companies alike.
It is brutal but do NOT hand in resignation before course start at the new company. Burn that bridge if You have to.
Regards
Cpt B