Moving from private wealth management to investment banking (london)

Hi,

So I am a recently graduated finance student from a non target wanting to get into IB. I  have one internship in private wealth management at a boutique firm in london and  networked a lot, had about over 50 calls however all haven’t really gone anywhere (tbh I haven’t really been keeping in contact with them as not sure how).

The feedback I have been getting from my applications is that my cover letter and CV are good however  not good enough compared to competition (for example someone had done their level 1 and 2 CFA during uni).

I recently got a job offer from the place I did my internship as an investment management assistant, as they are now recruiting  graduates (they weren't when I did the internship). 
 

My question is, how would I be able to move from private wealth management to investment banking. Would working in this company for a few years then do MBA to shift to boutique IBD be viable. Or should I take the job and continue networking to try get into IBD. I am currently 24 (did gap year).
thanks,

H