Can anyone help me get further with this? Each of the 26 letters in the alphabet stand for a number between 1 and 26.

I've figured out a few already but have made some assumptions.

N x N = M

I + C = W

Q + J = E

S x S = A

D + F = R + T

B + U = K

O x S = V + O

G x G = Z

P x N = H

Q x Q = X + L

C + L = Y

D + R = Z + P

F + T = (X*2) - A

B is lower than U

Z x N = 50

So far I believe that:

A=9

G=5

M=4

N=2

Q=6

S=3

Z=25

Any help towards a solution will be greatly appreciated.