Many thanks for your responses.
It would appear the transition from my earlier version of Firefox when I updated was not quite what Mozilla promised as several of the buttons were missing from the toolbar.
In 'Customise' there are separate black 'Stop' and 'Reload' icons, if dragged to the toolbar only the 'Reload' button is visible until a page is loading when it changes to a black cross as a stop button - as you said. Why they have gone from colour to monochrome for these I have no idea as they were far more visible before.
For the 'Progress' bar I have installed Status 4 Evar from your link and this provides an indication much as was present before.
Once again thanks for your help.