Congratulations and a big well done for getting your IVA pass.
Those guys at Cardiff certainly didn't give you an easy ride but you can be satisfied you've built a car that has passed the toughest inspection.
When applying for your registration don't forget that your dealing with civil servants and not necessarily kit car fanatics. A small picture story of the key build stages (donor car, donor engine removal, bare chassis, rolling chassis, engine installed, etc etc) should make it easy for them to understand what you have built.) I made up a little word document with a short description under each picture. A link to your Flickr account adds further evidence but you shouldn't expect them to have to wade through your thousands of photo's.
I also included a checklist of all the documents, forms, etc I included in the application.
Hopefully it will get done quickly to give you a few weeks of summer fun