Well, I seem to have managed it with destroying the watch.
I bought a rubber/plastic bezel remover from CousinsUK. It's a simple bit of kit and being softer than the steel watch, it doesn't damage it when it slips off. So, I'll let the pictures do the talking.
Bezel removed.
Click spring removed (care needs to be taken so as bit to damage the locating pin)
Locating hole for click spring.
Using a (slightly) sharp knife I worked it between the bezel and the insert.
Insert slowly coming away.
And.....
Finally, I refitted the click spring and bezel, then the insert and it now looks like this.
Quite pleased with myself as I usually work on much larger projects - like ships!