Hi Owen,
There is an index in the February Journal for each year, but I am not sure about an overall index. Perhaps someone else will chip in if there is one?
Another way you can search is to use the magnifying glass at the far right of the menu bar. This searches the whole website, including the Journals.
I will add fixing the Journal search to the to do list for the website developer. I am sure it used to work but I can see it does nothing now.
Best wishes,
Andy
British Astronomical Association
Supporting amateur astronomers since 1890