Hi @leeq
There is already a feature request for the Purchase Order creation from an invoice/estimate. You may wish to add your vote there:
http://community.quickfile.co.uk/t/create-purcahse-order-from-sales-invoice-or-estimate/13657
You may also wish to add your vote/comments to this topic, in regards to the templates:
http://community.quickfile.co.uk/t/purchase-order-advanced-css-html-customisation/8251?u=qfsupport