I thought 'Denton' would have given it away without the need for 'Mr. G', along with the extra clue that you mentioned, 'OF and H' and the David Jason connection.
I have all the series on DVD and the final episode was made with three different endings. The one that was shown on TV ended where Frost's colleague D.S. George Toolan died. I don't believe the episodes with the different endings have ever been aired, and strangely enough I have never watched those two either. Perhaps it's time I did. I assume one of the endings sees the demise of Frost himself so maybe I couldn't bear to think of that happening at the time. I must get round to watching them after more than 12 years.
I have to say it was probably my favourite series over those 18 years.
In the late 1990's I used to drive along the A143 yellow road on that map twice every weekday, when I travelled to Bury St Edmunds, where I worked for a few years, and back, and saw the signs to 'Denton' and 'Wingfield' and always thought of the series, which of course was airing at the time.
