Money.

The United Kingdom uses the pound sterling.

...best place to exchange Mu US dollars....

Read RS cash and currency tips: https://www.ricksteves.com/travel-tips/money/cash-tips

ATMs are the way to go.

Avoid (or at least minimize) cash exchange.

Then read: https://www.ricksteves.com/travel-tips/money/cash-machine-atm-tips

Pounds sterling, though with different banknotes.

English and Scottish bank notes are interchangeable. If you are going to Scotland after England, you don't need to change them.

As a side note, the 5lb note changed a few weeks ago. Make sure no one tries to give you one as they are very difficult to get rid of and they are not accepted. We got one from the tram ticket agent at the EDI airport and when I asked why it was so old, and he said it was still good. Don't take one.

Thanks Roy.

Roy, Teani, that's the £5 note. 5 lb = pounds weight, not pounds money, that would be very heavy money!
The new £5 notes are plastic and have Winston Churchill on the back.
Photo: http://d.ibtimes.co.uk/en/full/1521400/chuchill-sterling-note.jpg

Asking "Scotland is it Euro or GPB" is like asking if Alaska uses Canadian Dollars :-)

Best place to exchange is to use your normal card in an ATM, exchanging physical money always costs more.

The Scottish Banks have also changed to polymer £5 notes.

Together they publish this guide 'Know Your Scottish Banknotes'.