Imperial MSc Economics and Strategy for Business for London Finance?

Hi. 

I would really appreciate some advice regarding my situation. I'm based in the UK so would appreciate UK-specific guidance.

I did terribly in my A-Levels and ended up at a complete non-target university, so unsurprisingly I was constantly rejected for internships and was rejected from countless graduate roles. I graduated with a first class degree in economics, although this doesn't mean much since it was from a really low ranking university. I did manage to get on an accounting/tax graduate scheme and I'm currently in my first year of the graduate scheme where I've been completing the ACA as part of my role. The pay is pretty decent (especially for someone like me from a non-target university) but it's not what I wanted to do. It was the only offer I had and beggars can't be choosers.

I have received an offer for Imperial's MSc Economics and Strategy for Business programme and although this may not be the most elite programme out there, I'm really pleased that I've got an offer since it is a trillion times better than the terrible undergraduate university I went to. Also, I aim to apply for MBA programmes in America after 5/6 years and a Master's from Imperial will look a lot better than my non-target undergraduate university.

I'm aware that a decent Master's programme will not completely overshadow poor A-Level results and a non-target undergraduate university. After being rejected so many times during university, I have become extremely pessimistic and will not be wasting my time applying for elite firms/roles such as MBB or BB IB. I won't even get into a boutique IB firm since my chance at getting these types of roles ended years ago when I got poor A-Level results.

I shall be targeting tier 2/3 consulting firms, boutique consulting firms, corporate finance firms and Big 4 consulting/transaction advisory type roles. However, I'm worried that my bad A-Levels will still ruin my chances for these as well.

I'm 95% sure I'm taking the Imperial offer, but I'm really concerned that my bad A-Level grades will still hold me back when applying for jobs during my Master's. I've got a first class degree in economics and will have 1 year of experience in accounting/finance along with the Imperial MSc ESB, but since I would still be applying for entry level/graduate roles I'm worried my A-Levels would still ruin my chances.

I have passed all the ACA exams I've taken so far at the first attempt so in the worst case scenario where I don't get the offers I want during my Master's, I should be able to get another ACA graduate role/training contract and finish the ACA qualification.

Do you think my bad A-Levels will still hold me back when applying for boutique consulting firms/corporate finance firms/Big 4 transaction roles despite my first class undergraduate degree, my 1 year accounting/finance experience and the Imperial MSc ESB?

Is there a risk that the Imperial Master's programme doesn't boost my prospects at all due to my bad A-Levels, and that the Master's is just a costly way to make my CV look better over my non-target undergraduate university?

Thanks for your help. :)