SVA can be a nightmare especially if you do not have the backup of the manufacturer and know what to do and how to go about getting it through. So many things that come into the test now. You could end up having to rebuild it and changing all sorts of things just to get it through. Even the type approved CE markings on glass and lights are now part of it. So for example if your windscreen is not type approved, car will never pass. Than you have the possibility of ending up with a Q plate if you do not score enough points when filling in the spec / donor parts. Once on a Q plate, you cannot get any other reg on it and not the best thing to have on a car, especially if you ever come to sell it.
I think you need to look at the registration side of things with as much importance as the quality of the build.
Somebody on here must have some more info / experience of the current sVA rules.
When I built my Cobra I had to go through it and I was advised to build to the SVA spec, get it through and than start doing the changes. I remember the manufacturer had an SVA kit that they used to lend you to get the car through and so on. So on your own could be a daunting task.
Think this through and take good well informed advise.