Éclat doesn't exist. Three fictional branches - Marina in Dubai, Notting Hill in London, West Village in New York - built to make the multi-branch machinery real rather than decorative, the same way Amara Spa made a single Al Barsha address real.
A single-branch booking form is mostly a calendar. A three-branch one has to know which chairs are actually in which city before it offers anyone a seat in one. Pick West Village and the wizard only offers what that room runs - skin and brows, no colour, no blow-dry bar - and only the three stylists actually rostered there.
The chain, and where it's actually tested
Treatments stack, reusing the logic the barbershop demo already proved: a colour service and a blow-dry add their times together, and every offered slot is checked against the whole total, not just the last thing picked. What's new is the branch sitting above all of it - a stylist is only offered if she works that branch and practises the categories chosen, and a time is only offered if the total fits before that branch's own closing hour.
A stylist who stopped being valid gets cleared, not left selected.
Change an earlier answer - swap the branch, drop a treatment - and the later steps re-check themselves instead of quietly holding an appointment that no longer makes sense. A stylist who stopped being valid for the new picks gets cleared, not left selected and wrong.
What it doesn't do: take a deposit, send a real text, or check a real calendar. The 4-digit confirmation code is printed on screen, the 'already booked' slots are generated from a hash so the diary looks plausible without being one, and the prices are illustrative price points, not currency conversions at the peg. Every page says so, and both a noindex tag and robots.txt keep it out of search entirely.