They'll always be there if you're in BA. Otherwise they aren't so reliable.
The IPA offers exactly the same services for a fraction of the cost except they do not negotiate because they aren't a union.
Whenever I needed advice or help they responded quickly.
JliderPilot was referring to the IPA and my experience is the same. British Airways Line Pilot's Association were oddly silent when I approached them, not surprising as I've never worked for BA.