It's not free, but the new Curves card looks like it could be a good source of MS opportunities. It links to your card much like the Travelex Supercard does, but it also supports Amex! No fees for using it in your "home" currency, including no cash withdrawl fees! Abroad it's mastercard + 1% for purchases, mastercard rate + 1% + £2 for cash withdrawls
There's a one-off £35 fee to get the card (or you can pay more for unspecified future benefits...)
Full details are at http://www.imaginecurve.com/
In theory, you should be able to use http://www.imaginecurve.com/?r=GkbXE to get a £10 credit (and I'd get one too), only their referral system seems to be broken right now so I don't know... (They originally said http://www.imaginecurve.com/r=GkbXE but I believe that's wrong, though I'm not completely certain! It is a beta after all)
Three key bits to be aware of:
From the “What are the key benefits of using Curve?” page:
Pay no standard cash advance fees at domestic ATMs, across debit and credit cards.*
*Subject to fair usage policies.
Also, section 2.2 of the terms and conditions:
2.2 Your Business Account. Your Account is a Business Account. …… you attest that
you are not establishing the Account for personal, family, or household purposes, and its
use by you must be limited to business expenses.
It's iOS (Apple) only, at least for now