Welcome to the board, tomB!!!
That particular grill/gate you will eventually be able to open from the other side.
Go back to the large STONE snake - there is a brazier in front of it and perform the ritual which will cause the head to open and give you access to more of the temple.
And if you're really lost:
http://www.volberding.com/WHints/index.html
Xignal's excellent walkthru with maps!
Wyv