If I'm not too late I'd also like to suggest that you put additional
load spreading timbers, like two 4 x 2's under the feet of the bath if
possible.

My bath layed in the same direction as the joists hence two feet were
on one floor board and two feet were on another floor board. With a
full bath and 15 stone of body in it the floor boards would bend very
slightly and over a few years there was a moving gap at the wall side
of the bath.

Adding two 4 x 2's in the length dorection of the bath and under the
feet spread the load better. Resealing the joint and it ain't moved
since.

Chris.