Solved my problem of not being able to update the aspell path via the Editor Settings page.
The issue was caused because in my previous version (1.45) I had a problem finding aspell and I corrected this by adding the path to the config.php file manually. When I upgraded (1.5.2) and again had a problem with aspell I mistakenly assumed that the config.php file was the only place where the path info was stored. This is obviously not correct (although it does appear to be from where it loads its initial info) because after removing the aspell path line from the config.php file the Editor Settings (aspell path) is now working as expected.
I also noted that in the en lang file (editor.php) "spellcheck" is not included and therfore the button hint in the Editor Settings page displays as spellcheck
KS