I have a Garmin 1310t....less than £100 from most places....absolutely love it...never lost yet and never lost my car in an airport carpark...loads of features and comes with a traffic receiver which is brilliant....only down side is I think I am in love with the voice....I even talk to her.....
The best feature for me is if you get off course either by accident or design you get instant rerouting and I mean instant.
I suppose it's too simple to expect you have it in Mute mode...mine does have such a button.....or have you tried a different voice..japanese or russian sounds good...not helpful but sorry nothing else to offer. :-{
Thank you all for your answers, looks as though it will be a Garmin. Sipowicz, does yours send you away from Anfield and around Stanley Park to the Holy of Holies?