I believe an ATM card with the Visa logo if possible would be the best bet. In somewhere like London, there are tons of options for using a credit card, so if one place doesn't work, another might. In a small town like Keele, your options are far more limited! There are cash-points tho, so she should be able to get what she needs if she has an ATM card. Given most teenagers I know, the things she may want to buy are snacks, magazines, fast food etc. Not everyone is geared up for credit cards, and some will only accept them for transactions over a certain amount.

In addition, UK teens don't normally have credit cards, so she might find some shopkeepers suspicious of her using one. And you really do have to convince some places that they can take a non chip card (I've had shops produce old 'click clack' machines in order to do so!) which might be a bit much for a teen to do - you don't want to make life harder for her.

In terms of internet - data roaming is seriously expensive! What I always do is take out my SIM card when I get on the plane, and only use wifi for checking emails, the internet etc. Find out if the place she is staying has wifi, and go from there. I find most blackberries, iphones etc do work in the UK, but your phone provider can tell you.

In terms of spending, it does depend what is included (meals, transport, travel, entrance fees to places etc). If you can narrow that down, it may help to give more targetted responses.

She is going to have a blast!