Thanks everyone. I think Rateone's advice is worth taking. The last thing I want to experience is a diversion to a small airfield in northern France while our expensive hotel rooms remain unused!

The wasted cost is one thing, the stress and ruined experience is another.
On balance, Eurostar sounds sensible.
For the record, I expect to have accumulated at least 120 hours by the middle of August, including a number of trips with my wife, but I think commonsense rules in this instance.
Nevertheless, I shall enjoy the club flyout and perhaps my wife and I shall make the trip to Paris by light aircraft in the coming years, though I have to admit that the prospect of a private strip and night in a Chateau appeals!