LHR CH Treatments & Revivals Question

Traveling outbound LHR-MIA on VS "G" class reward tickets. Is it normal to book clubhouse beauty treatments in advance or is it first come/ fist served? Also, the MIA flight departs LHR at 11:30AM. Is the CH at LHR generally busy from 9AM-11AM? It will be a Wednesday.
And as for the Revivals Lounge, we arrive from MIA at 8:30AM and then have a long 1ayover. It will be a Sunday morning at LHR. I would imagine the Revivals lounge will not be very busy. Agree?
And as for the Revivals Lounge, we arrive from MIA at 8:30AM and then have a long 1ayover. It will be a Sunday morning at LHR. I would imagine the Revivals lounge will not be very busy. Agree?