Many thanks for the advice - I managed to change just the facia,with a new one by gently prising the unit out with a screwdriver.Changing the front panel was a bit fiddly,as there are numerous button contacters,that have a mind of their own,and given half a chance,move out of position,before you have a chance to push the new facia home.
The end result was more than worth it,even if it did test my patience!!!!
Rgds
Jerry