Keeprockin - If you'd seen the mess I made of my driving lesson before I took my test you wouldn't say I might have passed anyway!! And I wouldn't think Kalms are going to make you so calm you could be in danger of falling asleep, they just take the edge off. You're still totally alert, but you're just not completely debillitated by your nerves. You are able to be in control and put into practice what you've learnt without getting uptight and making a mess of it.
I agree that the examiner will take nerves into account but when your nerves are so bad that they are seriously affecting your chances, then you need to do something about it. I've never taken anything like this before and was sceptical but desperate enough to try anything. I agree it might have been a placebo, but something worked. Perhaps a placebo was all I needed - a bit of mental support, who knows? I still think it's worth a try.