ok, right, thanks for that!
Since ds nursery were continuing their illness imagining campaign I took ds to an emergency gp appointment this am to confirm he isn't in fact sick - just teething.
I had been looking in his mouth for evidence of proposed lurgy to no avail...but whilst I was there I noticed something else....
Apparently he has a really very abnormally low maxillary labial fraenum!!! Yeah I know! - ok so I googled.
Basically the inside of his top lip joins to his gum not a bit up his gum but between his front two teeth! How could I not have noticed this?!
I was expecting a gap between front top teeth as strong family history. But he has a BIG gap apparently caused/worsened by this! He did also have a tongue tie which was snipped when he was a few weeks - I wonder if conditions are related?
Will go and see usual Gp, but in meantime has anyone else had any experience of this?