If a Buy it Now listing with quantity more than 1 available is listed with 'simple' delivery now, there no longer an option to set a postage rate for each additional item.
Just confirmed with ebay chat that it is not possible to set postage cost for additional items. So will ebay charge full postage for each additional item or £0. The buyer will not know and probably will not buy
As soon as you overide SD by setting price to £800 and/or oversize, the option for additional item postage re appears
