Thanks for the responses. Looking forward to trying this out with eposnow and glad you had successes with them. Please keep us updated with your progress…
Since posting that idea, I’ve come across someone else who had the idea a while back, @pavel:
A super nice to have feature would be that of taking a snap and reading the bill, then I highlight different items with my finger (as Google Translate does when you translate from pictures), and it automatically calculates totals and assigns to friends to pay.
Bonus: @tom thought it was an “awesome idea”, so thats cool! Sounds like something could definitely be figured out between yourselves and Monzo 
Would be such a slick user experience!