How old is he ?
Why is he educated out of year group if he has "a mild SEN" ?
Yes, he should have a written plan - different authorities and different schools will call them different things, but there should be a plan (which some still call an IEP) - which should state what his targets are and what is being put in place to help him reach them.
Yes, they should be shared with family and with anyone who works with him.
Yes, they should be reviewed regularly (3 x a year is normal)
We have discussed an updated EP referral as the one from his last school is three years old
What happened when he saw the EP at his previous school ?
Was an EHCP Assessment request made?
Or was advice given and a decision taken by the Team Around the Child (ie, EP, yourselves, SENCo, class teacher, and any outside agencies that are involved), that an EHCP wasn't needed ?
I think the first thing I would ask for is a meeting, to address all these points. I would also be clearly minuting all answers - take a friend or family member with you so you can focus on askng questions if it makes it easier. (I do realise this might have to be a virtual meeting at present, although some schools will arrange a 'socially distant meeting' now).