I'm just posting this as a new thread as the original one has been locked. I
have found thought I'd found a fix for the problem posted by Jens Eeckhout which I had also had problems with. Original thread here: https://moodle.org/mod/forum/discuss.php?d=345085#p1391592
Setting up a single select autocomplete field in a form it always displayed the first element of the array on loading the page. I discovered from something mentioned in this tracker that adding 'multiple' => false in the options array appeared to fix this problem (even though false is the default value for multiple). However on further testing I realised that it does work, but as a 'multiple' which isn't what I need and despite 'multiple' being set to false.
So it appears that the problem is really with single select autocomplete. Any suggestions gratefully recieved.