queen mary flying start accounting or warwick gsd and business studies

It depends on how confident you are with ur career choice - the flying start sets you up for a pretty good headstart into accounting and having that name on your CV (if u ever wanna switch) will benefit you lots. Whilst Warwick is great and pretty reputable, there will still be difficulty in competing and having to get into the job market.
Going with PwC doesn't really automatically lock you into accounting either tbf, like I mentioned having the name will really help on your CV. If you would prefer to go Warwick (idk much ab it) then by all means do so, but bear in mind the long term too. i.e. getting into a solid career, being able to change careers, etc.

Good luck (: