We will fly from Liverpool to CDG using EasyJet which arrives at T3.

T3 is very far from T2 or T1. But the Roissy bus stop is just right outside T3. From the map there is ATM right near the restroom towards the exit.
My concern is in case the ATM(s) malfunction, we would be stuck as Roissy only takes cash from T3. Although at T2 there is window one can buy bus tickets using CC. However, it is a 50 minutes shuttle ride between T3 and T2 so it is not very practical. There are also plenty of ATMs at T2.

Once we get to town we would be fine as our BofA card can get cash from BNP w/o international withdrawal fee and would be our first choice. BNP is practically everywhere, and there is one right next to the Roissy bus stop at Opera, a few yards from our hotel.

So I think it would be wise to get some Euro before we leave UK. In sequence, we will be in London, Edinburgh, Glasgow, Liverpool and country sides in between.