If there are speed problem with the FileMaker database because all other possible causes were ruled out, there obviously are numerous possibilities; but very commons ones are related to unstored calcs.
I just posted a product feedback here tuesday which provide one example of them : search on unstored calc. I had a script-specific problem and luckily, could solve it quite easily.
But unstored calcs slowness, for instance in a list view, could be hard to solve because they are often structure-related.
Our developer has changes some of the sql calculations to the former way of doing this and this has helped the speed slightly.
Optimize formulas is obviously a good thing. But if a layout is displaying one or many unstored calcs and moreover, one or more of these conditions are met, it may not be enough :
- Huge number of records being browsed on main table
- One or more summary fields based on unstored calcs are displayed on the layout
- Huge number of records are found on related table implied on the formula
- The formula summarize one or more unstored calcs on related table
But maybe your developer already have checked all this and the problem is elsewhere...
You also wrote "4 offices in the UK". Are the databases accessed within internet ?