cheers lordcrocket , i was going to tell them i not paying the £65 pounds how can they justified charging me that amount just for sending me two letters!!

Hi there everybody hope you guys can help me, i was late paying my water bill by few weeks cause basically i just forgot about it ,then i got a letter from united utilities saying if i didn,t pay £190.34 within seven days they would take me to court and add other fees on top. So i payed of the amount i owned them, but now i have recived a letter from united utilites demanding i pay them £65 for fees and costs, and if i don,t they will take court action. should i pay them the £65? any help would be grateful thanks!!