For the first few months I was here, I was using my Fair FX cash travel card that I usually use for trips, which charges 1%, £1 and then a mystery amount something to do with the exchange rate, normally between £1-3. However, once I started earning and needed to withdraw a lot more often (I get paid into my UK bank account), these charges seemed too much to I looked into other options.
I started to use my Nationwide FlexAccount debit card which supposedly has quite good rates for withdrawing abroad but the trusty Servibanca cash points charged me around 8% when I used it and only allowed me to withdraw $300.000 (under £100) a pop. After investigating, the solution seemed to be to withdraw at Citibank which says it charges 3% and allows you up to $800.000 a go, but luckily I have only been charged around $12.000 and have managed to withdraw over $1m. The annoying thing about that though is that my Nationwide card seemed like it hadn't charged me extra but then the next day it adds around £5/6 charges to the withdrawal, so I actually ended up going overdrawn as I assumed all the charges would be all at once. So beware of this option!
So, after testing out many ways to withdraw money, I now have a Halifax credit card that charges me nothing to withdraw so long as I put the money back on it within 24 hours. I ordered it from here and got it posted it to me, which is risky but it arrived safely a few weeks later. So I now get charged the $12.000 fee from Citibank and nothing from Halifax which is great!