Not a rating or anything, but #DoctorWho is still the fourth biggest trending thing in the UK right now, and actually hit the top two spots earlier in the night also. Not quite sure what's particularly fuelling this but it's the longest the show has been trending for nationwide since the 50th anniversary episode aired (that lasted into the following day, and was trending worldwide for much of 23/11/13). By comparison
The Time of the Doctor was far lower down the trends, whilst
Deep Breath and
The Magician's Apprentice barely registered and weren't trending at all by midnight of their respective broadcasts.
The only other major successful trend the show has had in recent times is 'River Song' who has trended nationally twice this year - once when she was announced for a return, and at a random time earlier this year that wasn't reflected by any news.
Just bringing this up, as it's usually a sign of at least heightened mainstream interest (whether that is reflected in the overnights or the 7-day figures is yet to be seen). And long-running Twitter trends for television tends to be something that has gone down well enough for discussion. I suspect it's down to the draw from Maisie Williams - as great as I think she is in both Thrones and Who, I still don't get the mad fascination with her mind you

Oddly enough the Odin-in-the-sky thing seems to be very popular too...with many likening it to either Monty Python or the Teletubbies sun