Nib Technicians at London Pen Show - how to book

[Subtilior]

Hello, I'm new on here and planning to go to the London Pen Show in March.  I have a nib I would like to have checked over and wonder what is the way to have someone look at it at the show.  Is it first come, first served?  Do I book them when I arrive?  Do I have to book them before I get there?  Would I be better going direct to a technician and not bothering with the show?

If I have to book in advance, I can see the names of those attending the show, but being new to this, I do not know who is who.  The only name I recognise from the list is John Sorowka, whose name I encountered on this site.