As ballpark figures I would say:
~10% of students get a First
The next 40% of students get a 2:1
The next 40% of students get a 2:2
The last ~10% of students get a Third
A handful will get an ordinary degree (worse than a third) or fail outright. Pretty unusual though.
On these ballpark figures, most consultancies are interested in candidates with a First or 2:1 from a top university; which means they are interested in the top half of the class from a top university (or only the very best of a class from a lesser university).
Hope that helps with positioning your own qualifications accordingly. Tony