This question (or variations of it) has come up lots of times before but I have to admit to this being the first time I've heard Entropay mentioned.
The Entropay website suggests that their payment system is simply equivalent to using a Visa card (rather than a Visa Electron) one. However Martin Lewis's website states that "most budget airline flights treat this as an Electron transaction" (but, rather unhelpfully, doesn't say exactly which airlines do so):
http://www.moneysavin...irline-charges#elect1
2 years ago, MoneySavingExpert was recommending the Travelex Cash Passport as the cheapest way to get a Visa Electron card
http://www.moneysavin...blow-as-visa-electron
but (unless I'm missing something) they seem to have gone over to MasterCard now:
http://www.travelex.c...rt-currency-card.aspx
Chris