Today saw 9 optional updates. My free space went from 55.4Gb to 54.5Gb. I've since run a disk clean (including system files) and followed that by a restart and defrag followed by another restart. The disk clean took some 25 minutes in all and reclaimed only a few 10's of Mb. In other words next to nothing. This is typical behaviour of Windows Update although at some future point I expect to see a sudden jump back up in the free space allocation.