In reply to captain paranoia:
Yep. It appears that works well until the gate is replaced! Which is why it's posted in all the right places elsewhere.
The OP said "I hadn't phoned the coastguard prior to heading down as I had assumed (perhaps wrongly) they'd know there were climbers at BH in August..."
So he appears to have known about ringing before starting.
Then, oddly, he asks "I wondered what might be the best way to help prevent any more unnecessary call outs? I'll be sure to contact them before heading climbing next time!"
Locals should already know.
Visitors should check local guides, online crag guides, access databases etc to check whether there are any oddities or restrictions about access. That's what I do when I visit new crags in other parts of the country just in case.
As for Dono's "I know the book does state quite clearly to give them a call, I must admit I’ve never done so though, but haven’t done anything major there or in any areas where there are many members of public but I guess it only takes one", I don't think that's the best approach to avoiding Coastguard/RNLI call outs!