Just in case anyone has the facts to hand, what are the individual ratings for previous episodes which featured a Doctor's proper regeneration?

So that's:

Tenth Planet 4, ?m
War Games 10, ?m
Planet of the Spiders 6, ?m
Logopolis 4, ?m
Caves of Androzani 4, ?m
Time and the Rani 1, ?m
The TV Movie, which was 9.6m,
Parting Of The Ways, which was 6.9m,
The End of Time 2, 10.4m.

The Stolen Earth doesn't count.

Parting of the Ways didnt get much

The system now for monitoring ratings did not exist in Britain in the sixties, so it's unlikely that accurate data exists. BARB's figures only seem to go back as far as 1981.

Any ratings that could be found are all subjective to the time anyway... Less channels = higher individual ratings...

Yeah, if you're using them to gauge popularity rather than just being interested in the head count.

Using this page on themindrobber.co.uk which lists by serial only and not by individual episodes:

Tenth Planet, 6.8m
War Games, 4.9m
Planet of the Spiders, 9.0m
Logopolis, 6.7m
Caves of Androzani, 7.28m
Time and the Rani, 4.63m

So yes, this was the most widely seen regeneration by a comfortable margin.

I'd barely count the TV movie as a regeneration story, because the big thing wasn't the regeneration, it was because it was the first Doctor Who in years. I'd say the same of Rose if it had featured a regeneration.

My source is Wikipedia pages for the individual stories which list the ratings for each episode. Unsurprisingly the regen episodes scored higher than the average for the story.

Eccleston's last was shown in the middle of a nuclear hot summer, if I recall. I was away that weekend, and sunned myself very nicely.