Could a light helicopter pilot land a transport-category helicopter?
This is based on knowledge and a little experience. I have flown a Wessex to a hover and they are big, heavy, powerful beasts. If your example 


  our good friend Simon


refers to me, then I must also state that I only have about 130 hours so limited hours is more accurate :)

It is said that if you can fly one helicopter, then you can fly another.  Indeed, I learned on the R22 and it's a "fact" (insofar as if enough people repeat something enough times, it becomes a "fact") that if you can fly the R22, then you can fly anything because it demands careful handling and has very small power margins.  I have never heard a really experienced pilot refute that.

If we assume that you have enough fuel and that there is no complex fuel system which requires switching of pumps to keep the engines fed, then yes, you could land anything with one notable exception.

Nearly all helicopters have a couple, either manual or automatic, between the demand for power (how much pitch you are asking for) and the engine power output.  Raise the collective and the throttle is automatically opened and vice-versa.  This is certainly true about transport category aircraft.  On something like early Hilliers, I would need to learn pretty fast that as I increase pitch, I must roll on throttle otherwise, I will stall when I try to climb or raise the lever to come into the hover.  This is practised during PPL but I must admit, I've never used manual throttle control since I got my license.  

Another area of concern would be over controlling but that's easy to deal with.  I am now thrust into the pilots seat of a type I don't know and I am not licensed for.  I am going to land on the nearest safe spot.  I'm not going to do anything fancy whatsoever so, if I need a descent, I will lower the lever gently and use the cyclic to maintain my speed. Then I'll climb a little by gently raising the cyclic until I start to climb.  All helicopters fly nicely at about 60 kts so I will pitch for that speed. The only thing I need to look at to ensure the limits aren't busted is airspeed.  Any helicopter pilot would get the feel of this in very little time as would any fixed wing pilot.  It's just a question of how heavy the controls are and how much they physically need to move but that's quickly explored by starting gently and using just enough to do what you need to do.

Let's assume that the subject craft does have automatic throttle control. 

I will also assume that we are in VMC otherwise, we are all going to die.

There are only two other areas of concern that I can think of and that's the type of the landing gear (skids vs wheels and how many) and the height of your seat above the ground.

One major difference between rotaries and fixed wing is that there is no stall speed and all helicopters can land with the same forward speed and rate of descent.  I can, if I want to, bring the craft to a hover and stop to have a good think about what comes next.  To come into a hover is also easy.  You can do it by the numbers but the practical way is to keep your speed over the ground so that the site picture is apparently a fast walking speed and keep the landing spot in the centre of the window.  if the landing spot moves up, decrease your rate of descent and vice-versa.  Do this, and you will arrive close to the spot at a sensible speed and with a low rate of descent.  Vortex ring state won't be a concern for me.  I won't know at which speed I will lose translational lift but it will be somewhere between 10 and 15 kt, so I'll be waiting for that little shudder to start and the nose to swing a little, ready to bring in power and pedal.

I believe that most, perhaps all, wheeled transport helicopters have wheel brakes, but I will have no clue how use these.  So, I am going to land zero-zero and ensure that I am directly into wind and on a level surface.  The next think is how will I know when I've landed?  

When I first landed a B206, it was on my conversion course so I already knew how to land smoothly.  All I had to do to deal with the extra height I was sitting above the ground was "feel" the aircraft down.  It can be surprisingly difficult to know when a helicopter is fully on the ground and not flying it all the way down is one way to get into trouble.

I would deal with this by feeling for the first contact and then smoothly, but not too quickly, lowering the lever.  This does two things.  It ensures a firm contact and removes my biggest landing worry in an unfamiliar type which is dynamic rollover.  It won't be pretty and I might even get a blade strike somewhere but with power now off, we'll all walk away. 

So in summary, I wouldn't need any assistance but, if I can figure out where the transmit button is and how to tune the radio, I will try to get some anyway.