Thanks for the suggestions, I will have a look at those.
I have given a bit more thought about exactly what I am looking for (in addition to managing the DB with one of your suggested systems).
I want to be able to build web based forms that have a partially built query (specific tables / fields and records), users should be able to enter certain criteria.
Eg Allow a user to search for a country name eg GB
Then perform an update on all those records found to UK
Or to search all records where userID = user1
Then edit specific fields in each record found.
And with some forms, allow a user to export all records found as an excel or CSV file.
Basically - the sort of things that could be done with a MS Access form, built on a query - but web based.
I realise I could have specific pages / forms built in PHP to do these tasks, but would like to be able to use some application which will allow me to build the pages / forms quickly when I require them.
I think what I need is a query builder. I am currently looking at these, but perhaps someone could direct me to a suitable one.