This winter has seemed never-ending, but I have to say that braving the cold outside has been much more pleasant when not also having to brave the cold inside.
And now that it finally feels like spring, it is very comfortable indeed indoors. The heating has not been on at all for weeks, and the temperature sits at a balmy 20 degrees (+/-1). The sun comes in through the windows and the warmth stays with us for the evening and through to the next morning. The chill blast that awaited on emerging from the duvet is a thing of the past. It is most civilised.
Without draughts and cold spots, 20 degrees (or even 19) feels a whole lot warmer than it used to before the house was refurbished. I can remember sitting huddled in the warmest room at about 22 degrees and feeling just about ok until I moved. Now the whole house just seems to find its own temperature and it never feels cold.
My conclusion is that the Passivhaus methodology (for new build and refurbishment) definitely works. The house is behaving as it was designed to do in terms of comfort. Energy readings and temperature measurements so far back this up (but a year or so of further measurements will give a clearer picture).