Applying for accounting and finance

LSE states that for A&F, they want to see traditional subjects (you have this through Maths) and subjects that demonstrate analytical or writing skills. You don't have a subject that demonstrates this (at least according to them), so your subject choices would be considered less preferable. Your GCSEs certainly don't help your case either.
However, if you have no other aspirational choices, I would still apply. If your personal statement is exceptional and demonstrates real passion for the subject, there is always a chance, albeit slim. If you are not willing to take substantial risk and waste a slot, pass on LSE.

French is very writing heavy though so surely they would take that into consideration? Warwick is a good choice.

Writing-heavy is not the same as demonstrating critical thinking and analytical writing. I doubt French requires anywhere near the logical reasoning skills that is required in Economics, for example.
Plus, even if French required high-level academic writing, LSE doesn't recognise it as an essay-based subject, so it would be useless regardless.

Do you think I should apply with A*AA in Economics, Mathematics and Computer Science? Im stuck on what Universities to apply to because I want to stay in London and dont want to waste a slot on somewhere I know I wont go.