Users of the exchange, one of the world's biggest, said they were unable to withdraw or deposit sterling via the Faster Payments network - which enables mobile, internet and other payments between British bank accounts - or bank cards.
BBVA said that during a gradual roll-out it had detected a "significant desire" among investors for crypto-assets or digital assets to diversify their portfolios despite their volatility and high risk.
BBVA said it was limiting this new cryptocurrency service to Switzerland because the country has clear regulation and widespread adoption of digital assets.
Ether, the second-biggest cryptocurrency by market capitalisation after bitcoin, climbed to $4,372.35, eclipsing its previous record hit on Monday, and was last up 2%. Bitcoin was down a touch at $56,240.
US bank J.P. Morgan on Wednesday said the pace of evolution in the ethereum market has "remained rapid" and that there was still room for growth.