I'll use one of the many FX on line companies to get my Euros.
But you do need to be aware that using your debit card to pay for them may incure bank charges, the same as using a debit card to pay for euro's over the counter.
The best way to do it is to use internet banking and transfer the funds to the FX company, should be able to get 1.25 ish with no charges and free post over £500 as Jimbo says.
I'm off to spain golfing with the boys the week after I return from Agios Stefanos, going to change £3k to cover both trips and with the euro at 1.25 I'm almost getting my beer money for Spain free compared to the bad old days of £1 for 1.01 euro