I think that you may have provided the answer! I re-paired the 333 and 332 by pressing a single button on each device, and the missing volume control appears to have been returned to normal function.
And the standby sequence is doing what it’s supposed to do, too!
Many thanks to you and all the other Forum members who contributed their experience and expertise.
Now off to Cymbiosis to collect something beautiful - pictures to follow, no doubt.