Edit:

Well, don't I feel silly... And kind of smart -- just after posting, I had a flash of thought, and fixed it myself Basically, I'd forgotten to attach the new Collision to the Scene Root, hence it not showing :S This can be locked now

So you made a collision mesh for the portcullis that has holes in it?? That sound awesome .

I presume you're going to release it??

xD

Sorry if I didn't explain myself very well :S The Porctullis collision Mesh already has holes in it, and I wanted to take them away. Obviously if people particularly want that functionality, I can release it