importing

Hello, I am attempting to import and I have a shipper that can ship to me using air couriers such as UPS/FedEx/DHL from the USA to the UK but he uses a USA service for cheaper shipping rates that does not allow for PVA to be requested and also does not allow for the EORI number to be entered when booking the shipment. I have two questions for this shipment: 1. Can he manually write my EORI in the empty field on the three copies of the commercial invoice when he attaches them to the parcel? Would this be allowed? 2. If I am charged DDP VAT from the courier company then can I still reclaim the VAT if I did not use PVA? Thanks for any advice on this as it's hard to find info on this.