Your going to a target. If you put the effort into it, you can easily land any position you want.
The difference between sales and ops is pretty much everything, how come you are interested in both? Not sure about your interests but if I were you I'd definitely go for sales, it's exciting, provides much better paid/exit opps and you are also a female. That being said its obviously not laid-back: going out with clients on your 5th night in a row is not exactly fortunate.
Remove these:
X School London, UK (you'll need to add Teaching Japanese into your Interests row to still include it on your resume)
Saturday Literacy Scheme London, UK
Teaching 10-11 year olds about writing and presentation is nice and all but don't add much value to your profile, it's banking: sure it makes you interesting and it's good exp to have but you already got that point ticked with the Romania thing. You'll also be able to come up with these in your interviews so it's fine to remove them.
Also remove "Head Girl", you'll be able to expand on this anyway, see competency interview questions.
Make the Interests row compact:
- Latin and Ballroom dancing, Math (if they ask you to expand on this THEN you'll be able to say "Royal Institute Saturday Maths Master Classes", so no need to write it out fully) , Teaching Japanese, Organizing school events
You don't need to add
too many details on your exp (as you did with the interests section) -> the purpose of the resume is to make the person reading it interested in you so they'll give you an interview.