@Edward *******
they have an appt booked,
as long as they have those forms filled out (Form 1 the TM7 application, Form 2 the Terms and Form 3 the overstay acknowledgements) along with their copies etc done they should be fine,
but you're correct,
no harm going early (although they usually won't let you in early).
Personally if I had everything filled out, signed all my copies I wouldn't even queue up at that "Stage 1" but just walk right up and show the appt print out at the next stage where they give the queue number to get in the office
I thought I saw a sign about people with appts last time I was there too.