With a little help from a friend I've improved the search to as far as I intend to whilst retaining a single search box format.
For interest? - I'm developing the database offline through some custom software and uploading to the web at intervals. This allows me to make global changes easily if necessary but more usefully I have a spare field to insert relevant keywords where required.
The data was fairly straightforward to compile before 1961 when the industry consolidated and mergers and co-operations became the norm and well known names spilt into many different divisions. (Avro 748 HS 748 BAe 748 etc )
I'll have the data set complete by the end of August and then change the main emphasis from search to a classified directory.