in my opinion if you are going to plan to fly in IMC in the UK, you need a full IR, and a de-iced fully equiped twin. Anythig less and you are taking a real risk.
That's rather a sweeping statement for what actually encompasses a multitude of conditions. Some of these do require what you say, but others, in all honesty, don't. Flying is all about risk management and reduction. I would take issue that all these conditions constitute a "real risk".