Sorry to hear about,and disappointed to hear about the bad experience with Etihad. I looking at flights going the opposite way,from Asia to the UK,and back via BKK.And I'm not exactly spoilt for choice(and ridiculous prices) due to the Ukraine and airspace situation.
Chances are you've already researched it: One thing that I've found helpful on SkyScanner is checking prices for one way tickets with different carriers.Used to be that a one way ticket was the same price as a roundtrip ticket.But not any more. Makes for a really flexible schedule, depending on the carrier(s).
I hear what you say about arrival times. Arriving back in the Uk in the evening and having to get home at that time is not only tiring/tiresome but also depressing as hell!
Arriving in BKK early afternoon or anytime in the morning is best for me. I like arriving in the morning because chances are I'm going north to Chiang Rai/Chiang Mai or south to Hua Hin.And can still arrive at my final destination with some of the day remaining.