On my drive to work, I drive on varying surfaces, from really rural country roads through to the A16, and I can tell you that regardless of the quality of tyre (I use Continentals), it is the road condition that dictates grip-ability, along with MUD. For example, Hurdletree bank is notorious for a bad road surface and it isn't unusual for my car to over-steer even at low speeds on the bends. At one point I actually thought I had a flat tyre as my car seemed to slide sideways at 25mph, only to discover the surface is really crap.
On the flip side of the coin, the A17 has an excellent surface which instils a certain confidence when overtaking or going round a round-a-bout.