I dont think you could dispute the court costs and sols fees as unreasonalbe they are fairly standard. (Any other thoughts anyone?)However I think you implied that you paid before court action is that right? In which case the charge has perhaps not been made.
Water bills are similar to council tax the whole years bill is chargable at the begining of the year the option to pay installments is a concession if you dont keep to the installment plan the provider will eventually seek remedy via the courts for the whole balance.
National debtline have some great information about water bill follow this l
ink It sounds like the water may only be your most urgent problem, they were extreemly helpfull and supportive to me. The service is free
Good Luck - DS