what is the best way to set up headlights for sva test??

don't bother do it on the day.

Yup. As long as its quick and easy to do they'll let you fiddle during the test.

I took mine for a "MOT" before the test and did it then but its not necessary...

Don't. worry about it, as said above you can probably do it during the test. In fact during ours, the tester actually tweaked them for us.

you can get it roughly right by driving your tintop up to the garage at night with the lights on, and make a note of where the pattern falls, then do the same with the kit car.

its not precise but at least it will show you tried.

I set mine up like that - park the tin-top about 30 feet from the garage door, stick masking tape where you see the 'cut-off' on the door and then replace tin-top with toy car and tweak as neccessary.