Hi LJ,
I take on board what others have said; it is not always helpful to compare yourself to others working for different firms, on different projects and with different experiences ...BUT I do understand why people want to (admittedly I like to myself all the time.)
Including my peers and other Consultants I know (2-4 years experience) having been recruited on established grad programmes, our range is from £33-40k.
-I know a few who earn significantly more than this and they managed to secure such a rise by moving to a new firm after they had got a few years behind them.
If, at your company, you know for certain the pay band for someone with your experience is at the £31k mark then I guess you are being underpaid by this company's own standards.
If you can honestly see no reason why your peers are earning more than you then I guess it's time for you to think about moving on.
I am sure, with 3 years good experience you can achieve a higher salalry elsewhere.
Hope this helps and Good Luck!
:-)