To register you'll need your Excise Registration Number. This should be the warehousekeeper excise ID. This is a 13 alpha-numeric character reference starting with GBWK and can be found on your approval letter.
The warehousekeeper excise ID is the consignor/consignee reference. The warehouse excise ID is the place of dispatch/place of delivery.
If you don't know your warehousekeeper excise ID you should contact the National Verification Centre on 0141 555 3616 or email email@example.com.