Q:

How to avoid having a snorer share your dormroom?

So every few months I go away for a weekend with a large group (100 people give or take). We generally sleep in a camphouse, which has dorm-like accomodation with a few bunkbeds per room.
There are a few notorious snorers in the group. Previous experiences have made it so that I would prefer not to sleep in the same room again.
Last time, we arrived early, so we (me and my gf) were the first to claim a room. There were two beds left. Then someone, who is a known snorer, came and asked whether the beds were still available.
This is a tricky situation. I feel like it would be unpolite to flat-out lie about the beds still being available, but similarly, allowing would cause their own problems.
I personally am not a light sleeper (I'd describe it as being in a coma), but during the process of falling asleep, snoring can be pretty disruptive. This would definitely cause similar problems to the folks nextdoor.
How can I tell them that I don't want them to share my room without being offensive or impolite?

A:

I feel like it would be unpolite to flat-out lie about the beds still
  being available, but similarly, allowing would cause their own
  problems.

You're on to something here. Telling someone that you mind their snoring might be offensive, but lying to someone always is. It lets on that you don't think of them highly enough to give them the truth, and it can come back to bite you badly.
I sleep walk from time to time, and occasionally even talk in my sleep. To my friends, this is distracting and can ruin the quality of their sleep. There is nothing offensive about telling me this directly, unless you phrase it like it's a character flaw. So I recommend something like:

Yes, these beds are still available. I have very light sleep though,
  and you're a bit noisy when sleeping, so it would be nice if you could
  find another bed in the camphouse.

This isn't inherently offensive. It's as non-offensive as you can get in these situations. In fact, most snorers will appreciate that you're telling them why, because the one thing that hurts more then being rejected is being shooed off like you're not even worth the explaination of it.
I definitely recommend against lying, if it comes out (and it will) they will feel insulted and belittled by your lie.

A:

I was in exactly your place years ago. I tried several things but in the end the real solution was this:
Approach the organisation, explain the situation, and propose to introduce a 'silence room' for light sleepers.
In addition ask around for good candidates to fill it, and have a covenant about noise during the event. Ours was, early night or undress in the bathroom and sneak into your bed without speaking. The same for getting up early. Worked like a charm! 
And because everyone was in on it the room was tagged clearly before people arrived, chosen for being off the beaten track, away from the toilets & bar. 
Never had any problems about snoring after that either, I forget because snorers are usually solid sleepers or some other reason.
To handle snoring it is also best to be open about being a light sleeper. Last time I shared a room with a snorer we agreed that I could prod him and clearly say 'stop snoring'. But he was a real social guy and knew he would:

Turn half-asleep, stopping the noise
Continue sleeping

It saved my night. But this was a veteran snorer, it will not always be possible to take this road, especially in a silence room.
Generic advice:
Explain your problem, agree upon an approach that saves both your nights. Often that will indeed mean different rooms.

A:

As a snorer, and I've tried plenty to stop it, just be honest and upfront.  Let them know that you have trouble sleeping when there is someone snoring. It's rare that a snorer doesn't know it, and while it is frustrating to be told this, it is definitely better than the alternatives - being woken through various means, or another not getting sleep.
Normally, people can learn to filter out repetitive noises, and if you can't, that's no more your fault than it is the fault of the snorer that he snores.
As long as you are honest about it, it's the best way to go.  If you were to get caught out in a lie, then that is most definitely hurtful, and may be taken as if there was another reason for it, which neither party will want, and can hurt relationships.
In this situation, I would recommend trying to fill those empty beds beforehand if possible, as "they are already taken" when true is typically not hurtful.
I'll note that if you do end up sharing with a snorer, please don't wake them.  As they were asleep and you were restless, they will likely drop off again before you do, unless they force themselves to stay awake, and then when they do sleep, they may wake you again.  This becomes a cycle and ruins both your sleep patterns.
Try earplugs etc, and if you still can't sleep, it is better to talk to them in the morning to discuss solutions (they will be in a better mood if they slept too) and change arangements for the next time.
They will usually be sorry for keeping you awake and be happy to change rooms etc if possible.

