Splott Man speaks truth, Inkberrow.
The thing about accents here is that it is a border area, culturally.
Just to the North West , the accent is distinctly Black Country, to the North East, Brummie. A few miles east and you are into the rural burr of Warwickshire and the Vale of Evesham, and to the South is Worcester itself which is where West Country accents start. South East you have The Cotswolds and the Oxfordshire way of speaking. Further West, Herefordshire and the Borders sound definitely Welsh.
Add in the fact that Worcestershire, and the Malverns are a popular retreat from London an the site of many Public Schools, and that high-tech industries attract people from all over the country, and you have the basis for my statement that the accents you hear on the Archers are authentically North Worcestershire.
Cheers
Dave
(PS. I know two people locally, one liveing next door, who speak Ruth Archer Geordie)