Firstly, fibreglass is quite robust and easily repaired.
Second, as has been pointed out your insurance may cover this.
Thirdly, you should also consider pursuing this amtter with the original builder.
Finally Homebond cover water ingress, as opposed to water from internal leaks, so you may be covered.
The leak may be arising because there is no stepped flashing between inner and outer leaves - assuming this is a cavity wall.
Or it may be because the flashign does not extend sufficiently to the side of the bay projection.
Alternatively it may be arising because there is no DPC tray under the 1st floor window above.
Simple stipping back a well-done flashing will not expose a fault that lies behind the flashing within the wall.
A quick google search using "Redwood Park bay window problems" only found this thread.
This supports what another poster has stated that the houses seem to be well built.
ONQ.
[broken link removed]
All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.