I may be misreading but are you advocating VFR on top in a SEP is okay, or was that one of the events that occurred due to unforeseen circumstances?
Over the span of my flying career, VFR on top in Canada has gone from being not legal, to legal, when properly rated, planned and equipped. I advocate flying within the regulations. That does not mean that sometimes things happen, but advanced planning to operate outside the regulations, your capabilities, and those of the aircraft, is just plain wrong.
So your standard equipped light aircraft has enough instrumentation that flight without reference to the ground is possible, but that does not make it safe or legal. There is usually a minimum redundancy designed into these systems, but you have to be a pretty sharp pilot on instruments (read IFR rating here) to manage well on partial panel, if you even recognize that's required after a failure.
I'm not saying that it cannot be done safely, there are obviously many who do. As the original question seems to have centered on amature built aircraft, I hold the opinion that they are one step further removed from the design requirements necessary for redundant systems, and truly safe IMC flight. That does not mean it can't be done, but I would expect that those who have a firm grasp of the practical, and regulatory requirements for the aircraft, probably would not be enquiring generally here (no disrespect intended to the original poster).
Climate plays a role in the circumstances conducive to icing, and I agree the summer in the UK is less conducive than Canada generally (though you are further north than I). That said, my second scariest icing encounter ever was day IFR in a Twin Otter southbound over Nice, France in August, during which we literally fell, while maintaining our attitude, through about 6000'. Yes, we had allowed swiss chees holes to line up, and thus were partly the cause of our circumstances, but it still happened fully legal IFR. Then, later in the flight, over Africa, where ice was not much of a risk, the instrument failures began. Flying an ILS down to minimums in a sandstorm, with nothing more than the magnetic compass for heading reference, is not too much fun either!
Last fall, while flying a Hughes 500D helicopter down from Alaska, I was reminded that fooling with the weather is a really bad idea in a poorly equipped aircraft. This helicopter had no gyro horizon or attitude indicator, no turn or slip indicator. It had a compass, ASI, altitude, VSI, and the engine instruments. That makes you think long and hard about what you need to be able to see in front of you in flight!
IMC is not to be tinkered with. Either stay out, or properly prepare, equip, train and file for the flight. I hold that generally light singles struggle to maintain the minimum of "equip".