Had to load an earlier save [SPOILER(S)]

[dunno]

Spoiler below!

You can get all of the ingredients both before or after the Shadow blocks the Transept and Choir. The blood can be gotten from a drain in the room off to the left of Agrippa that was walled off before the Shadow hit, or (like you found) in the drain in the Transept.

The poison mushroom can be gotten in the choir before and just outside the choir afterward. The meat can be lowered into two different wells, the one outside the Transept or the one that you face right after you escape from your prison cell (in the same room as the diary that gives you the flashback of the farm house).

Right. I had both the other ingredients, but wasn't aware of the other drain.

So it is a perfect game..
Thanks