On a self defence course with MA group, we trained a few of these scenarios..
Here's one I did:
We were sent into a house where our suited up [full padded body suit, groin protector etc with helmet & face shield] instructor would attack us at any time. I was told to stand in a room with eyes closed until he chose to attack. We had to respond to the attack and were allowed to give him the works, we could do anything, knees, elbows, kick and punch as hard as we could, no holds barred and we had to do it like it was a matter of life or death. The referee ensured there was no cheating and that we stopped when we were supposed to.
He tackled me from behind, in a running rugby style tackle, pinned both arms to my sides and then lifted me off the ground!
The only thing I could do was kick for his legs, stomp at them, use my elbows and wriggle about a lot until I freed one arm. Then I managed to turn and started boxing his ears with palm heel strikes to the side of the head. Once I got my other arm free I gave it to him in the face as well and managed to knock him to the ground after several hard ones. During this time I also managed to get in several good groin kicks.... and a few to the lower legs
The referee had to drag me off before I really started to hurt him.... [IMG]http://www.fightingarts.com/forums/ubb/biggrin.gif[/IMG]
The thing is with all of these attack scenarios, you have a split second where your brain goes "eek! I'm being attacked what do I do???!!" - before the conditioned training mode switches on and you react. Getting the reaction time shorter is the key to surviving.
One major thing I've learnt from this is to always keep alert and keep my hands high so they will never get trapped like this again!