Thanks for the link russian-dima, some great examples on your website and I have added it to my favourites for future reference.
However, my code did work but I realised that this line:
.eq("monthYear", title)
has changed to:
.eq("title", title)
meaning it was searching the wrong field. No clue how it happened but I have returned it to the correct value and the dropdown is now working correctly.
Thanks for taking the time to respond and support - I am sure your website will come in useful as I continue to develop my website 
This one can now be closed thanks!