You,re welcome
Generally speaking ( lottery scenario as it seems to vary from 1 DVLA office to another how the requirements are interpreted to fulfill the registration process ), when sourcing parts from various donors as you seem to be , if you don,t go down the "New " current registration route then you will probably be given a "Q" registration for your Roadster.
Have you got the latest downloadable "IVA Manual" ? this will help during the course of your build, the classification of the Roadster is "M1" within the IVA manual guidelines.
We like photos on here
cheers
andy