Identify a sci-fi anthology episode about alien abduction to a 'white room'

I am trying to identify an episode of an anthology show from the early 2000s. It may also be a made-for-TV movie, but I don’t believe the plot was long enough to support a movie. I’m confident of all the details below except for parts in italics.

Plot:

In present day America, a man is having recurring dreams about being experimented on by aliens. In these dreams, he is paralysed/restrained on a gurney in an all-white ‘infinite room’ surrounded by medical equipment and surgical tools. At the end of these dreams he always wakes up in his own bed with full memory of events.

He tries to convince others that he is being abducted but he can’t prove it. He might visit friends, psychiatrist, etc. At some point he encounters someone who gives him the ability to consciously control his sleep. I think this took the form of a pill, but it might have just been willpower.

As a result, the next time he has a dream, he’s able to wake up during the event, and find that the white room is real. He fights and escapes his captors, and takes several xrays from a rack as proof that the events were real. One detail I recall clearly is that the xrays had a large alphanumeric code on them.

Somehow he finds a door at the edge of this infinite white room and opens it to find himself standing outside a nondescript warehouse at night. He’s jubilant that he finally has the proof of his abduction in the form of the xrays, but when he looks at them, they’re distorted and garbled. This is purely as a ‘gotcha’ to the main character, it isn’t explained, and the episode ends with him distraught and alone.

Other details:

• Shown on UK TV at some point most likely between 1998-2004, on BBC.
• Almost certainly a US or Canadian production.
• I don’t believe the characters or setting recurred in other episodes.
• Almost certainly not an episode of the 90’s The Outer Limits, since I’ve rewatched them all trying to find these scenes and couldn’t find it.