Hi Chris
As Huw says, switches need not be a problem. Go on to
Registration and SVA and read through and get yourself an SVA manual. Don't listen to hearsay. When you are ready, put the car through the test and they will tell you what needs to be done by failing the car. Put these things right and it will pass. I have never heard of car not being able to get through the test.
If you need more advice and encoragement join the GT40 Enthusiasts Club if you are not already a member.
Brian