In all of my recent travels we have had no trouble finding ATMs. Since we want to be in tiny villages and remote places in Scotland , we are concerned about the availability of ATMs. Also Do most small pubs take credit cards nowadays?
Both the PLUS (Visa) and the CIRRUS (MC) networks have online worldwide ATM locators, which should help you find the answer to your first question.
This is not so much an answer at a bit of additional information regarding money in Scotland. This is of a year and a half ago. You will be getting currency (bill) issued by three different banks: Bank of England, Clydesdale Bank, and Royal Bank of Scotland. All three are equally accepted in Scotland. If you take Clydesdale or Bank of Scotland bills to England you might as well assume they are going home with you to put in your scrapbook. Places in England that accept Scottich currency might exist along the border, but that's it. Beware, my friends.
On the other hand, I've never had any problem using English pounds in Scotland. From what I understand, it doesn't matter if the money's from a Scottish or Northern Irish bank. It's all good and should be accepted throughout the UK, but some small British merchants don't like the Scottish (or Northern Irish) pounds because they can't tell if they're fake or not. If this ever became an issue for you, you could just take your weird Scottish pounds to a bank and exchange them for English notes. Or vice versa.
For the most part ATMs are all over Scotland. On the Outer Hebrides you may find that you need to get money in Stornoway or Harris. If you know exactly where you are going or have a general idea of some areas to ask about, check TripAdvisor. I went to Scottish Forum and then searched on ATMs. This gave me several threads to investigate. Also, you can post your own question there. TripAdvisor has locals answering this type of question. Their answers tend to be more accurate and current. Pam