Thanks for the reply :o) very helpful. Just noticed the price to tax the thing, ouch!

Actually the KV6 and K four pot engines have little in common, bar the naming convention. The V6s don't have the poor HG failure reputation that the four pot engines do. That's not to say that they don't fail, all engines have head gaskets go occasionally, but the reputation of the four pot units means that greater attention is attracted when this happens to anything with "Rover" and "K" on it.

The serious woes of the K are more prevalent on the 1.6 and 1.8 versions. Those use what Rovers called "damp liners". The K was never intended to go beyond 1.4 litres and Honda engines were supposed to cover that range. The BMW purchase scotched this. Taking the K out to 1.6 / 1.8 left insufficient webbing in the block to support wet liners, so the liner sits in an extended casting at the bottom end, is completely surrounded by coolant at the top and is clamped into place by the head. Hence "damp" liner, half wet, half dry. The biggest problem caused by this arrangement is that any movement of the crank with the head off and without securing the liners first with the correct securing bolts can easily dislodge the liners. The fact that the head gaskets fail mean that they are far more likely to spend time with the head off than most. Couple that with the irresistable temptation to rotate the engine while the head's off.......

The V6s were designed as 2.0 / 2.5 units and use a conventional wet liner arrangement with the entire liner held firmly by webbing from the block walls along their length.

I won't bother to contradict you over the head coolant capacity, bar to say that there's a wealth of material to support that this is indeed the root cause of failures in the four pot units.