I fairly infrequently drink wine, so haven't really noticed the 500ml and 200ml sizes. But I do remember that in the past some bottles were 700ml while some were 750ml. I think they're all standardized on 750 now, is that right? With that difference and the 62ml between a half litre and a pint, you're only getting/losing about half a glass, which seems, well, half-glassish. My prognosticatering (otherwise known as cynical guesswork) is that many UK-bottled wines will switch to pint, charging an extra ~20% for the larger size. After a while, they will return to the half litre but keep the new! improved! price!