spree_paypal_express/app/models/billing_integration/paypal_express_uk.rb

class BillingIntegration::PaypalExpressUk < BillingIntegration
  preference :login, :string
  preference :password, :password
  preference :signature, :string

  def provider_class
    ActiveMerchant::Billing::PaypalExpressUkGateway
  end

end