I agree with growin - I don't think this is Ceanothus.
Photo 1 is my photo - note the curled leaves and yellow 'stameny-looking' things shooting out from the flowers.
Photo 2 is by cypres from the internet images for Ceanothus thysiflorus 'Snow flurry' - the leaves look different and the flowers don't seem to have the yellow stamens as in photo 1 - Yes?
I just can't put my finger on why I don't think it's a Ceanothus. I did a good couple of flats of cuttings last summer and I guess you kinda get to know the plant when you do that. I looked at all of the images I could find of white Ceanothus and I noticed the centre of the bloom looks different. Something about the veination of the leaves - not sure what it is. Some other suggestions: Leiophyllum buxifolium, Phebalium