On the subject of escort availability, over the last decade If you look through the RN news history, you will see that Type 23s and Type 45s (in particular) have been maintaining currency by escorting US and French carriers on a very regular basis. In future, the only difference is that they will have a UK carrier to escort.
On Tier 1 confrontations, it has long been UK policy that this would only be done with allies. But the UK aspires to bring a credible component to that allied effort, and in doing so have some say in its direction. Most likely is a confrontation with a proxy.
A QE with 24 F35s all its compliment of ASW /AEW helicopters and escorted by 2 Type 45s, 2 Type 23s and an Astute is a material contribution to NATO and any other allied mission.