Martinm

Donor reg and chassis number don't go on to a kit. You need to download the IVA application form 

https://www.gov.uk/government/publications/iva-application-form-for-passenger-cars-iva-1c

Chassis number can be applied for prior to the test from DVSA, reg number is assigned once you've passed the test and begin the registration process.

There's all the info you'll ever need in the IVA section of this forum. If you plan on doing the test, you'd be wise to have a read through a few of the threads.

Thanks for the info but what is the point in having a donor car if you can't put it on the kit

The age of the donor car will dictate the age related registration that the DVLA issues you with for the kit car, assuming you have used enough of a 'single donor' to qualify. In the old days (certainly SVA era) you could retain the original donor car's registration number but that gave rise to the large number of incorrectly registered and non tested kit cars that are regularly seen today.

Of course, if you aren't using a single donor the car will get a Q plate anyway.