Hi
As I understand all this, open to correction etc.
Have a really careful read of the full rules for aircrew again, you are correct that in thinking you are not exempt from quarantine
but you have an exemption that allows you to leave quarantine to perform training/duties assigned by your operator ..
The body of the rules in part state that for Amber list countries (e.g. France):
If you live overseas you must quarantine in your accommodation while in England, except while you are undertaking the exempt activity or travelling as part of your work.
If you are in England for longer than 2 days, you need to take a mandatory workplace, community or home
lateral flow device (LFD) test on or before days 2, 5 and 8 after arrival.
If you are travelling every day, you must take a lateral flow test at least once every 3 days.
(my italics/bold).
Further down the rule states that this applies to:
Pilots and crew, as defined in paragraph 1 of Schedule 1 to the Air Navigation Order 2016 or other people carried to perform duties assigned by the aircraft operator or pilot in command relating to the safety of passengers or the aircraft, where they have travelled to the United Kingdom in the course of their work or are otherwise required to travel to the United Kingdom for work purposes.
(my emphasis)
So as I understand ..
1. Carry ID, letter from employer.
2. Travel into UK - you do need to complete a Passenger Locator Form (PLF).
3. Go straight into self isolation on arrival at the place you nominated on your PLF.
4. You can leave isolation only to perform duties such as your LPC
5... and also to go direct to the port of departure to leave the UK once training /duty is complete (that is contained in another section of the more general rules).
Hope that helps