Force display of other currency than default?

[Kennett Square]

Hi there ladies! , I have scoured the vast ocean of zen cart related posts and cannot find the answer to this relatively simple problem:

What I hope to achieve:

Default/base currency: GBP
(currency in which I buy from the supplier and base my pricing on)

Displayed currency: Only EURO
(customers only in euro zone)

I dont want the customer to have the choice to select currencies, so I have gotten rid of the currency drop down. How do I get zen cart to always automatically display EURO when the a customer visits the store and not the default GBP.

Seems simple enough, maybe I have been a bit of a noon and missed this one!

Thanks in advanced