Joey has been in great form for the last couple of days.  Played really nicely either by himself or with Izzy.  No significant over-reaction.  Energetic without being manic.  Funny, imaginative, affectionate. 
Why the change?  Not 100% sure.  Perhaps the diet is kicking in.  We have spoken to him about the over-reaction and emphasized that, now that he is 10 years old, he cannot do this - and also warned him that as of today, we would be having a zero-tolerance policy towards it.  We have also spoken more to him about his early days and even shown him the street where he was born - amazing what you can do with Google Earth now!  He is off school for 2 weeks, which no doubt helps. Whatever the reasons, he has calmed down and seems much happier.  Let's hope it continues.