Nigelh,
I agree that more accessible and complete IMC training would be appropriate, but you would only stop CFIT accidents in poor weather if was a compulsory part of the PPL. Even then I doubt the average ppl could or would even want to keep their IMC skills current. The same would apply to a low time CPL trying to break into the industry.
I can see where you are coming from with the getting through a band of weather scenario. I'm sure it could work in low land England where there are plenty of sources for accurate weather. But in upland England, Wales and Scotland, those sources are few and far between. Additionally weather tends to be more localised, so if you used the IMC option, you might have a lower chance of getting into your private site than you perhaps would have done staying VFR.
The IMC below MSA point I was trying to make earlier relates to trying to get up a valley where the bottom is clear of cloud and the ridge clamped. Hence MSA being a 1000' or more above you. Going IMC is clearly not an option, which is the point I was trying make.