Pre-booked on the 8th June. Upon enquiring today the dealership confirmed a booking number.
Compared to the booking number I had for my 9th gen Civic through the same dealership, only the alpha numeric dealer code is common (K03):
K03-130**** (10th gen)
K03-009*** (9th gen)
Other members in this thread have posted first three digits 202, 402 and 801 for their 10th gen bookings.