Big4 to MSc Finance options.

I'm currently a first year Audit monkey for a Big4 firm, my training contract has me complete 14/15 ACA exams in the first 8 months of work. Outside of this we've been sent in for a few months of work during our firms busy season.

During the busy season I found that the nature of Audit work was not quite what I wanted and came across as not analytical enough, really I was spending 80% of my time chasing down clients and ticking boxes rather then producing anything meaningful. As a result I'm looking to do my 3 years in Audit and then perhaps reskill with a MSc in Finance to pursue another, more technical finance role. Though I do understand that it's entirely possible to make the jump to ER, TAS etc straight from Audit I want to rebrand myself with a more prestigious degree first.

My main question is with the following "attributes" what sort of courses can I expect to reasonably be accepted for.

-Somewhat weak 2:1 Maths degree from a semi-target (Nottingham), though my 3rd year results were 65% ish.

-14/15 ACA exams done in an 8 month period + a few years of work at a Big4

-GMAT score of 710

-CFA Level 1 <- Though this is yet to be sat/passed and feels like it might be redundant.

I have a feeling that my degree feels like somewhat of a limiting factor which concerns me. Though would I be wrong to assume that I have a reasonable chance of getting into weak targets like UCL/Warwick but Oxford/LSE/Imperial would most likely be a shot in the dark without some seriously strong extracurriculars to back it up and a compelling GMAT score (730+)

As well as this when it comes to Extra-curricular (or the work equivalent), what sort of things are these Universities really looking for? My current plan is once I finish off my final ACA exams to start writing my own limited ER reports (NOT on my firms clients). Then essentially testing out my report recommendations by simulating a small hedge fund (say 100m initial). Though I would most likely 'invest' in securities outside of just those covered in my ER report, especially if any strategy I employ necessitates a more complex portfolio. 

Any advice would be more than appreciated.