I couldn’t say for certain

Uh...uh, possibly - I couldn't say for certain they haven't. Oi [why?], what's brought this on?

Uh, uh, possibly. I couldn’t say for certain they haven’t.

I think the other guy says All right [or perhaps oi], let’s wrap this up.

Uh...uh, possibly. I couldn't say for certain they 'aven't.
Oi, what's brought this on? (Oi here is a British dialect equivalent to Hey.)

Blue JayOi here is a British dialect

Ambrige, the town that this radio soap drama is developing on, is probably not the real regional name in UK. Is there some hint in their dialect that denotes certain UK province?

Yes. It is set in the fictional county of Borsetshire, which is said to be located between Worcestershire and Warwickshire, which are real counties next to each other south of the city of Birmingham. The accents of some of the characters are typical of country folk in Worcestershire, southern Warwickshire, and the counties to the south of them. The people in Birmingham and other areas to the north