Laguna airbag light flashing?

I recently suffered a timing belt breakage, resulting in damage to a valve and the head. After changing the head in my 2 litre, 8 valve N reg Laguna, and connecting all the obvious wiring plugs, the car starts fine, and drives as it did before the break. However, the airbag warning light starts flashing a few seconds after the engine starts, and continues to do so while driving. I know there's a connector I haven't plugged in, as I found the wire spring - which keeps the plug and socket together - under the car when I moved it.
The question is, where are the plug and the socket (they must be in the engine compartment somewhere)? The plug is probably dangling down somewhere out of sight, but I just can't find it!!

Help, please.