£52.50 for being overdrawn - Co-Op

wimblewomble_2

I dont know if I am being too picky about the charges, but....

I have a business account with Co-Op, run in credit for 5 years, and last month was overdrawn for the first time.
I was charged £35 for being overdrawn.
And a further £17.50 for being sent a letter telling me I was overdrawn.

I accept the error, but not the charges.
The letter was a computer generated letter, not a personalised letter written by a "real" person. How can they charge me £17.50 for a letter, when ALL other computer-generated letters cost next to nothing?
(I get 2 or 3 a month ordinarily, and they DONT cost £17.50 per letter)

Anyway, am I being picky, or is it ok for me to get fussy about the charges?

thanks