SRowells Black Rallye

[powerandtorque]

Firstly, should there be some sort of plug blocking these holes?

Yes - it's a black plastic plug with a T40 torx drive. Part number 517914 from Peugeot (with a silly MOQ I seem to recall)

You're unlikely to snap the front nipples - the problem with the rears is that it's a steel nipple in an alloy casting, so suffers dissimilar metal corrosion. If you let the rears drain dry when you changed them then you will likely need to bleed the fronts through as you've potentially got air in the system now - not only that, but it's good practice anyway.

Removing snapped bleed nipples is a pain, because you have to remove all the old nipple and not damage the seat that the nipple screws down and seals against, which is all too easy when you drill out the remains of the old nipple.