The UK embassy will reissue the COE if you send updated airlines, dates or times.
As you have already been issued a COE, all official boxes have been ticked. The ASQ will also reissue the booking if you are a day or so adrift.
The revised COE arrived back the same day as receiving my request for some similar changes on my return.
I would suggest holding off to see which other airlines/countries may modify their UK specific travel rules.
Thailand appears to have revised it's entry requirements on the IATA site:
IATA - International Travel Document News
MK's post on the airline thread also: