i work for scottish power part time selling gas and electric whilst im at uni
there is no dif in annual bills between SC and NSC if u are an averge user.
standing charge - u will be charged a set rate every day plus one rate only for each gas and elec unit u use.
No standing charge - u will be charged a higher rate for the first 225kwh elec used in the quarter and 1143 for gas used in the quarter. Over and above these ammounts u will be charged a lower rate, usually much lower.
pay attention to the unit rates and not whether it is NSC or SC
if u are a really low user use NSC