I don't know how the Italian registration works, what i would do is go to the DVLA site and find out where the nearest SVA testing station is, then give them a call, they should be able to advise you what to do next. when people build kit cars they test them and if they pass give you a SVA certificate. fill in the registration forms and they'll issue you with a Q plate number, get as much information about the SVA test because its quite expensive and more intense than an MOT, Let us know how you get on.