Please keep us updated before you proceed to the next stage, whatever that stage may be. If they refuse, demand specific points as to why and let me have a read. If they comply, you are NOT subject to any fees, re-stocking charges etc. You are entitled to a refund of cash deposit, finance payments and damages to the value of your part exchange.
Of course, the other option is they hand you another new Polo as a replacement. Same spec etc. if they have one in stock.