Thank you everyone for your help.
I rang the dealer this morning, at 1st I was asked if I needed more time to save up the extra AP!!! I said no I don’t need more time because I’m not paying any extra, I’m paying what was agreed at the time of ordering, as is stated in our emails. He said he would look into it & get back to me asap, within the hour I had a call back saying they would honour the original AP.
So happy!! I’m excited to collect the car Wednesday.