Tricount really would suit you and your friends down to the ground.
You can enter various currencies. For example, if someone bought a round of coffees, when waiting for the Chunnel, they’d enter their bill in GBP. Then if another bod, picked up a round of drinks in the bar in Calais, on night one, they’d enter their bill in euro. Then on day two, if someone picks up the lunch bill in Dijon, they’d enter it in euro. The app makes the currency conversion, taking everything back into the home currency, presumably in your case GBP.
Similarly, if only two bods out of say the eight of you, picked up a debt that didn’t invoke the other six, the app allows them to say, “This debt is only for me and Andy”. The app will make the adjustment, leaving out the other six fellows.
Then at the end of the trip, the app gives a suggested division of the various debts and provides an accurate / fair basis of who owes who what. Likewise, it displays the same each time an expense is added. It is a thing of genius, equal to the propelling pencil and shoe laces.
PS You do NOT need to use the credit card that Tricount now push. Nobody I know does. It’s no different to say, Amazon or a host of others, pushing their cards. Just ignore it.