There are various rules regarding displaying of prices, depending on the final consumer. If you are dealing with the UK and/or EU market, then pound sterling plus euro would possibly be advisable.
Also remember to provide the price plus vat rate applicable to the final sale.
I use a number of on-line international companies, and in most cases they provide different currency acceptance, due to their banking arrangements. PayPal/eBay (as an example) have a facility for conversion and international payments or receipts.