Thanks so much for the swift replies!! I'm completely obsessed with Dan Cruikshank's programmes and loved the Brasilia church - also liked the building in Kazakhstan!
Unfortunately it's not the one you've kindly posted links to either, but like the look of that one too...!! I came across the one I'm thinking of completely by accident in an architectural book a few months ago and forgot to make a note of the name of it. To me, from memory it reminds me of a thatched cottage... I'll keep hunting!! But thanks.