I personally know of several cases here in Germany where continuing flight into adverse weather conditions by non IFR-rated (but obviously capable) pilots has resulted in accusations of "endagering the safety of an aeroplane and its occupants in grossly negligent manner". The prosecutors/authorities have won every time.
That seems to be a very German thing.
What exactly were the circumstances? Except in obvious cases, like departing VFR into an ATC-assessed OVC002 (and bear in mind and doing so into OVC006 would be prob99 legal in UK Class G because you can fly at 500ft AGL), only the pilot can know his actual flight conditions.
The FAA has also successfuly prosecuted pilots for "VFR in IMC" but only in such obvious near-airport cases.
Maybe the German accused just pleaded guilty, like a good citizen should
I'd caution IMC holders to think very carefully before planning an international flight in dubious weather conditions. It's terribly easy to be tempted into pressing on and once the trap is sprung, you can very quickly run out of options.
I learned this the hard way and was lucky to escape with my life. Not being prosecuted & getting to keep my licence was an unexpected bonus.
Can you describe what happened?
Legalities aside, IMC is the same in the UK as France etc. There is no obvious reason why you should get killed in France (e.g.) and not doing the same thing in the UK.
I would not suggest somebody embarking on an obviously illegal flight, on the basis of the IMCR, but that is a different line to saying that somebody might get killed when using the privilege abroad.