Once a verbal offer has been made what is the process and timescale?
Can't answer for the timescale, as there are any numbers of variables, but the offer will be made formal via UCAS. So then the applicant needs to accept it, and then get back to the university about accommodation, and so on.
But all of this will be communicated in writing by the university - generally by email.
I'm in a Department which is never in Clearing, but I used to be Head of somewhere where we went to Clearing a couple of times (we picked up students who'd done better than expected, in the days before Adjustment).
I generally aimed to have things mopped up by Tuesday of the following week at the latest. But we generally only needed about 4 or 5 extra students, and they were keen to come, and wanted to get it sorted.
But it could have changed - once admissions caps are off, there are many more applicants, and much more volatility in the system.