I'm in Scotland too. Enquire are very good if you call them as regards to your rights and supports in law.
It is difficult to know what's going on with the info to hand. Is he ok with friends - will he still go over to pals' houses, play out, have friends over?
Does he still engage and get involved with friends? Is he ok going to cubs, beavers, any other groups?
Is this definitely just school?
Does he seperate well from you to go to other activities?
Sometimes kids school refuse because they are worried about YOUR health - that something awful is going to happen to you. This is the kind of age kids become aware that parents can die.
Has anyone at school had a parent die recently or become very ill? Any child at the school very ill or passed?
Any health concerns in the family? Grandparents?
If all that is ruled out and he goes off to other activities with the same friends, you need to look closer at the school environment.
The teacher.
The toilet situation.
The class control.
Next - you mention handwriting. How are his other motor skills? His pen hold? Getting changed for PE? Tying laces?
Some teachers put a lot of pressure on to do things fast and if your boy is dyspraxic, he will struggle to process verbal info fast and slowness getting changed, messy handwriting, poor organisation still gets some teachers really angry. They shout at the kid which causes anxiety and poor self esteem.
Anything like this needs an educational psychologist involved and an IEP in place.
Other clues to poor motor skills are a dislike of ball games, messy eating, clumsy, might have an unusual gait when running - arms out maybe. Balance can be poor and might be scared of heights, avoids rough and tumble type games.
In fact any learning prob needs the ed psych.
Emotionally based problems (worries re home, friends etc in the absence of a learning prob it's clinical psych)
Clinical psychs are nhs based and chances of seeing them next to nil. You would need to go via gp or private.
Ed psych are education service - school can refer.
Start with Enquire. They will point you in the right direction