PO and Invoice currency diffrerences

Hi

We have the following questions

1. A PO is generated in currency GBP for a supplier site which has invoice and payment currency both EUR

          Is this allowed as a standard functionality

2. The invoice is recd in EUR for the PO raised in GBP

          Can the PO and invoice be matched (as inv=EUR and PO=GBP)

         

3. Invoice recdeived in GBP for supplier site currency EUR

          Will it allow me to pay in GBP

          Will it allow me to pay in any other currency

Any notes or documents highlighting this are welcome

Thanks

Ninad