Here are two scenes which remain as outstanding queries as far as identifying the actress involved goes. Usually with uncredited roles there is nothing to go on which helps in any way, but for the two I've listed here my research has uncovered some possibilities to consider.
Grease Monkeys (BBC3/2003)
Comedy Drama Series
UPDATE: This has now been solved - see post 18th Jan 2014 - Grease Monkeys Update.
Frankie Boyle's Tramadol Nights (C4/2010)
Stand-up and sketch show
In episode 2 of this 6-part series, there was a Doctor Who pastiche entitled "The Time Travelling Professor" in which a college professor and his student companions travel in time and become stranded in the past. One of the companions called "Terrence" is seemingly a man replete with a beard but in the end turns out to be a woman and opens up her shirt to reveal she has breasts.
She had some dialogue, however, the cast list only included two female names who are both known and neither were the one playing "Terrence".
Listed Cast for episode 2: Frankie Boyle, Jim Muir, Tom Stade, Robert Florence, Thaila Zucchi, Laurence Saunders, Kirstin McLean, Kevin Guthrie, Albert Boat.
The name "Albert Boat" only appears in episode 2 and I can find no references to this person being in anything else, so it is possible it could be a pseudonym.
On a casting website I found one uncredited actresses called Eleanor Gibson listed for "The Frankie Boyle Show" in 2009 (which the Kaleidoscope guide says was the working title for Tramadol Nights). She lists herself as being a "supporting artist (in) various sketches". Because of the male disguise makeup the woman in the sketch was wearing it's not possible to spot a clear resemblance (or conversely be able to definitely rule her out) and so this is currently only a very low possibility based purely on her being the only uncredited role I've found for this series. There were other sketches throughout the series with miscellaneous parts that she might alternatively have been part of, and the likelihood is probably greater that it is not her although the possibility remains.
Here is a face picture of "Terrence" from the sketch. If anyone does have information on who it was playing "Terrence" that would be useful.