Q: Can't see all my iCloud photos on iPhone

I can no longer see around half of my iCloud photos on my iPhone 6, although they remain viewable in the iCloud itself.

All my iCloud photos disappeared from my phone last week when I signed out of iCloud Photo Library in an attempt to restart the uploading process, as my pictures had been stuck on my phone and not gone into the iCloud for a couple of months.  However, and without doing anything to remedy this the last few days, around 1400 photos were put back onto my phone last night, from the iCloud - all the pictures which I have taken with my current phone.

Therefore, is there a way in which I can 'bring back' the remaining photos (i.e. the ones which I had taken on previous iPhones, are in the iCloud, and which were previously on this iPhone)?  Before the breakthrough last night I had previously tried the usual solutions (i.e. switching iCloud library between on/off; plugging in my phone; wifi connected) but had had no joy.  I have also spoken a great length with Appple Support on this matter.  The iphone is the only device I have.

Be grateful for any ideas