Ah right, but nah, mine wasn't a fancy Airfix kit or anything like that, it was just one of those die-cast things.  Out of curiosity I just tried looking for it based on what you wrote and, lol, I actually found one on eBay!  That part you just did in the last render used to attach to the bottom, and there was a button on the side of the body that you push to fire it (spring loaded).  If you look at the underneath photo you'll see a slot, and that's where the part you just modeled used to slot in, you can even see the fire button on the other photo.

I remember when I had it, my dad used some really strong paint stripper on an iron gate, so I waited until he went to work, poured a heap of the stuff into a bowl and dipped that toy plane in it.  It actually worked, came out all bear-metal shiny and I thought it looked really cool!

Anyway, if you're curious, Click Here to see the model it was before I paint-stripped it :-P
Oh, and thanks for the memories!