A day later - it's taken hours, but the photos are now restored. A word of warning to others using a combination of Blogger on Android and Windows. It seems that posts in draft on Android over-write finalised, published posts in Windows. So, if you draft the post on your mobile, but publish it using your computer, you are left with drafts on the Android version. The natural inclination is to delete them as a published version now exists. If you do, the published version gets deleted too.
I won't do that again.