For me, it’s always been cheapest to use an ATM at my destination, and let my bank do the currency conversion instead of using the rate offered by the ATM. My bank charges me something like max(5€, 1%), which is usually substantially cheaper than all the other options. I think this is more or less the same (or cheaper) for all German banks.
Almost all UK banks charge 2.75% above the visa/mc wholesale rate for overseas transactions. Plus they usually charge 1%-1.5% for overseas ATM transactions.
This is so prevalent that it's common for new banks (or existing banks doing a push for their new current account) to offer commission-free overseas spending. But many of them have pulled the 'perk' after they've gained a large enough customer base. If I recall correctly, at least Halifax, Nationwide and Metro Bank have in the past offered accounts with no commission on overseas card transactions, and then changed the terms to the standard (2.25%-2.75%) after 1-3 years.