Pre-IPO equity in a PE-backed software business: what happens to the sweet equity at listing?

I am the first reward hire at a private equity backed software business headquartered in the UK with about 1,100 people. A listing is planned within 18 to 24 months. The top 35 managers hold sweet equity that pays out on an exit under a ratchet, and another 200 people have options that vest on exit.

The sponsor will sell down in stages, so there may be no single exit event. I have been asked to propose how the existing arrangements convert and what the listed company plans look like.

For those who have been through a listing: what converted, what was locked up, and what did you wish you had settled earlier?