I suggest you look at the build thread of Dougy. He's in Southport and put his motorised bike through SVA. It's not as hard as people think, you really need to just make a motorcycle that will pass an MOT.
This is the latest VOSA SVA sheet I could find, and most of it won't apply to you. If you have it below 50cc it's a bit easier, and if you accept a restriction on speed and output, easier still.
Queries should be directed to Chris Corker at this email.
No stealth measures are going to effectively disguise the bike, and if you have an accident on an uninsured/untaxed/unlicenced machine and you survive, the courts will bounce up and down on you.
This bloke's been there and done it as well.
And LEDs are ok for lighting if they do the job.