Disappearing - ghost - imessages from myself and spammers

This one seems to have Apple foxed. Regularly, upon turning on my phone first thing in AM, I get notifications either from my Apple iCloud email or what seems like real UK mobile numbers (I am a UK resident). I cannot open the messages, they disappear from notifications upon signing into my phone, and they leave no trace in iMessage either on my phone or iMac. I have taken note of some of the numbers as they show up on watch notifications screen. Searching for the numbers with Google normally throws up negative reviews and possible scams. This has happened over nine months and across two phones I have owned in that period. I can go weeks without notification and then a whole bunch at once. Often I get multiple notifications at the same time - and they seem to be duplicates. The other day I had six from one phone number all at the same time. Apple has been through every possible change in settings. No one at Apple support has heard of this before. I await Engineering.... but I am not expecting anything. I saw a similar thread dated 2020 with many me toos marked.... anyone have any ideas?