I have an offer from a big 4 consultancy, but 2 offers from smaller ones, but for alot more money (20% more). Advice please?

Size isn't everything. Money is.

Seriously though, it depends on a whole host of things like what is important to you, who the small consultancies are and who the Big 4 is.

For example, some small firms have better reputations and abilities in particular niches than large full-service firms. But if you're looking for structure and order in your career path then a Big-4 accounting-based firm will probably be better suited to you.