Greetings to everyone. I am now posting my findings, having presented my work at the Conference this week.

Method
The external stimuli I decided to use were recordings of speech, one in English and the other in German. This represented two stimuli that differed in semantically meaningful content.
I had all of my participants first spend at least a few weeks trying to improve their dream recall abilities, an important and necessary step in any dream research. Luckily, everybody saw noticeable improvements, especially in the amount of detail they could remember from a dream.
The main experiment took place in our Sleep and Cognition Lab. My participants were given the opportunity to take a morning nap for 2 hours, while their sleep was monitored using polysomnography. When signs of REM sleep appeared, I played one of the stimulus sound files and then awoke the participant to obtain a verbal dream report. Using this technique, I was able to get a dream from a total of 9 of my participants; some had trouble sleeping in the lab, but this is a common issue in such research.

Findings
All dreams contained conversation or speech of some description, but unfortunately we cannot confirm if the stimuli were responsible for this, mostly because my participants could not remember the exact word they remembered hearing in the dream. Despite that, there were at least two dreams of interest to suggest direct incorporations of the stimulus.
One participant reported hearing a muffled voice as he was walking down corridors in his old school. He couldn't remember what it said, but his imitation of what it sounded like was very close to how the English stimulus sounded, so therefore I am confident in saying that that was the English stimulus making its way in the dream.
Another participant dreamed about relaxing and sunbathing on a beach with her family. She came to the conclusion that she must be on a foreign beach and all the other beach-goers were foreign based on the fact that they were all speaking a language that wasn't English. Sure enough, I was playing the German stimulus at that time.
Four participants dreamed about actually trying to get to sleep in the Sleep Lab itself, a common dream experience in a lot of lab studies (Schredl, 2008). I am interpreting this as evidence for the Continuity Hypothesis of dreaming, that we dream about what we do and think about in waking life. This is evident in these lab dreams by the fact that participants knew they were in a sleep lab and had to recall a dream for the experiment. Something I observed which has never been observed before (as far as I know) is that 2 participants in these lab dreams consciously anticipated the stimulus, even though they didn't know what it would be at this time in the experiment, and attributed events in the dream as being the stimulus. As an example, one participant reported waking up in the dream in a place that resembled a classroom, and there was a big board at the front playing adverts on a loop. She explicitly thought to herself that that was the external stimulus, therefore she knew the stimulus was going to happen at some point and continued to process this salient thought into the dream.

Similarity of dream experience was assessed using Q-Methodology. I extracted three factors from the data, conceptualising the range of experiences in the participant sample. 5 participants had dreams which were calm, consistent, and slightly emotional; 2 had dreams which were emotional, but normal and understandable; and 2 had dreams which were inconsistent, unrealistic and unstable. The most contrasting statement in the sample was "Things seemed stable and consistent in my dream", ranked most highly in Factor 1, the lowest in Factor 3, and was irrelevant in Factor 2.
Even though this configuration of factors does not clearly support my hypothesis that external stimuli can reliably induce similar dream experiences, the application of Q-Methodology was a success. I was able to extract naturally occurring categories of dreams based on their subjective experience directly from the data. What's more, my participants found using Q-sorts to report their dreams to be very helpful, allowing them to think much more deeply about their dreams and consider aspects of them that they may not have thought were that important compared to free recall. For these reasons, I highly encourage more dream researchers to make use of Q-Methodology.

That's it. I hope that this has been interesting and insightful to anyone who reads it.