I have posted this before regarding Travelex at the airports.
As an experiment, when we landed at Heathrow 2 in April, we used our Schwab card at the Travelex ATM there for a minimal 20GBP withdrawal. When we had a chance to check our bank records, we found the debit was $29.84 USD (or 1.492 per GBP), which was a markup of we are not sure, as the published interbank rate for that date would have meant a debit of $29.85, the rates were dropping during the day. For the charge to have been as high as 1%, we would have been debited $30.13.
And bigger surprise, DCC was never offered. This went straight to GBP.
Based on this, it should be fine to use your debit card at Travelex ATMs, at least in Heathrrow where there are no bank ATMs. If you use the Cirrus and Plus ATM locators, you should see that there are ATMs on these networks in almost all the major European airports.