It was gone teatime when I noticed no spots at all on 10m. Then I saw the PC had closed the WSPR program to install updates so I had not actually been on 10m WSPR for some time! This may have been several hours! Doh!
Anyway, at 1900z I restarted the PC and did a time resync and started up on 472kHz (630m) WSPR. No great DX so far but I am being copied in the Sheffield area (IO93) and am copying a Dutch station. Nothing special but I am definitely on 472kHz WSPR! I shall remain on this band overnight and switch to 10m WSPR after breakfast.