I was on this last night and according to Open Train Times we were due to run through Bristol Temple Meads and stop at platform 15 for an hour from 0155 to 0255. Instead we rushed through platform 10 and then presumably stopped at Exeter to stay there until the scheduled departure. I know this because by change I happened to go to the toilet as we were passing St Philips Marsh, and stuck my head out of the window expecting us to stop. In addition as we sped through a member of station staff hurtled out of his office and had a suprised look on his face as well. I take it this was a last minute change of timetable?
As far as I know the sleeper always goes through Bristol TM, never stopping, it normally gets into Exeter (especially on a sunday night) a round 70 early,
I think the main reason being is that the train really has no reason to sit a round at Bristol as the crew will all be based at exeter, (driver and TM)
I think mainly though with 1c99 they just want to get it down to the south west as quickly as possible and then very slowly take it from their to Penzance, Also Passenger comfort, not stopping at Bristol is one less "jolt" to wake all the Pax in beds up,
But yeah, as far as I know both the Up and the down sleeper never really do stop at Bristol, even though sometimes they are timetabled to,
Funnily enough though when the Down runs Via West bury it is meant to stop there, but it never does.
However the Up sleeper does always seem to stop and Westbury for about 15 mins (if not running late) and also Swindon I am told to?