2015 Forester - Radio tuning!!

[Glenikins]

Embarrassing problem:

On taking delivery of my new Forester last year I tuned in various FM radio stations on the audio system and all was well.  Until that is I went on holiday to the other side of the country.  Or rather, until I returned home.  The next day I selected Radio 4 and was rewarded with nothing but static.  Ever since, the system has steadfastly refused to store the local BBC4 channel.  Try as I might (including reading the manual) I have been unable to resolve this and it's driving me to distraction.

Any help or advise would be much appreciated.