The hybrids simply have enough electric to travel the EU test distance and thats it.
After that they are lugging around several hundred kilos of extra weight, decreasing their efficiency.
However, its all done on those magic few miles and so "its greener" and less tax (for now).
Everyone I know with a plug in hybrid never plugs it in, usually because they can't at home or at work.
Its rubbish and until this technology is meaningfully better, I'm not going anywhere near it.