Thanks for your help Bob
I had wrongly assumed that the reset function would put the phone back to its state when I bought it. I've uninstalled Kaspersky but I'm not sure it's all gone. I've now got to work out why, having done the "normal" unlock phone process, I go straight to another key entry screen which requires the Kaspersky password before I can access the phone's functions. Not too clever when the phone's ringing.