Flyer 19832007 - understand your point but from experience on a few occasions - if you wait for the e mail it generally arrives after or at best contemporaneously when dates are promulgated, hence no dates left when you log in.
If you're interested and cogniscant of the seniority issue, I don't believe there's any way round putting the effort in to getting the first available date, work commitments notwithstanding.
Best of British to you