According to the UK Defence Journal blog the timeline is very sporty - by Summer '22 with approval from the CAA and MAA. That should narrow it down a bit.
Any ideas to buy the 100 Sqn Hawks and contract them back to the RAF has been scuppered by the air-to-air radar requirement.
Perhaps it's an attempt to flog off the Tranche 1 Typhoons and get a contractor to fly them; that will help to reduce the JPANs at Lossiemouth and save in the short term as pilots will ET and join the new company. But then the hard-pressed TG1 techies will jump ship as well ... not so good.