Very good question
I think it is possible but dependent on the following areas:
1.What industry you have been doing IT consultancy for e.g. if you’ve been running banking IT projects you will have both a wealth of knowledge about this area and probably be able to produce a good CV noting relevant experience to enter banking post MBA. However if you have been working in other areas it maybe difficult.
2.Was your experience more technical or business orientated? I am assuming the latter; if so cherry pick the projects from your Big4 days to make yourself seem more attractive to a perspective MBBB or banking employer.
3.Good academics, it’s amazing that after all your experience, firms will still look at A-levels, your degree and where you did it. Unfortunately there is not a lot you can do about this, but they will be looked at.
4.An MBA can be used for a career change but you will need to get the best GMAT score possible and also attend the best B school you can get into. The better the B school brand the more you will find MBBB and top tier banking organisations sniffing around for prospective employees.
As far as what position in banking I am not sure, perhaps if your target is front office maybe a more financially focused qualification such as CFA would be more appropriate. Anyway good luck and I hope it all works out for you.