Seeing as far as you know.. it's a once off thing.. "GO FOR IT".
If you don't someone else will...this could be an opportunity to prove your self to this company as a skilled, motivated and competent Helicopter Pilot.
They may well remember your attitude, dedication and professionalism,
when a job does come up...hey presto.. you got the call in.
If these opportunities are every so often, then you've got nothing to loose.
If this becomes an all day everyday thing... then they should pay.
This is a good thread...as this is a real life situation every where in the world...everyday.
You just have to know the line and when your being used..by cheap, tight arsed operators.