I then searched the internet for a decoder. There were a lot of hardware decoders but very few that could decode audio input to the soundcard. I then found clock1.1 from F6CTE which was easy to install and has a choice of time signals it can decode:-
One point to note is that after being installed the programme auto launches into a calibration routine for 3 minutes during which time there is no spectrum display. The following shows a complete time sequence reception:-
Admittedly this solution is not the most cost effective. Last year I picked up for $1 an Oregon scientific WWVB clock, with LCD display and alarm functions for $1 from the local charity shop!