uk insurance

does anyone know a good cheap uk modified car insurance for a 19yr old driver who will have 5 years ncb ( due to current insurance)? also do you have to inform insurance companies at start of year if you plan to do mods within the year, or do you phone up and tell them as you do them. obviously paying the extra. i have heard that some companies dont mind what modifications you have up to a certain value of the mods.

thanks