Thank you so much everyone 
I will refer to this post before the next show or pony club camp and be much better prepared in future.
Pony's behaviour was vile yesterday morning - rearing and trying to barge/jump his way out of the stable when he thought he was missing something. He had two (very experienced) pony club mums cornered
They belted him and got him calmed down and under their control but it was awful.
Today, we got there early. Bathed and then walked and walked him round outside in the yard. Took him in, tied him up in a corner and tacked him up early. Then made him wait until everyone else was out whereupon DD led him out herself nice and calmly and in control.
Riding, he has been really good!! And he's good at home, though he will bang the door and stamp on occasion. But oh, I was all for selling him yesterday 
I think we have decided to keep him, but will work on making him better mannered. Ineed more confidence myself.
Washing up liquid and baby wipes have been used prolifically these last few days - will look forward to trying everything else.