Does any country ban VMC on top flight under VFR in its airspace?
In the USA, and countries which have modeled their regulation based on FAA regulation, VFR-on-top is an IFR clearance, and requires an instruement rating, an IFR compliant aircraft, and operation on an IFR flight plan.
VFR over the top, however, isn't...and is perfectly legal. In the US, there's no prohibition againt flying under VFR without an instrument rating, provided one has the requisite cloud clearances (distance from clouds) and visibility met. The irony is that this enables a pilot to fly under instrument conditions (eg between layers with no discernable horizon, or at night with no moon or references. In my opinion, a clear shortcoming in the reguirements of the regulation, which the UK has addressed and the FAA has not.