The couple, who began making sails in Crosshaven over 20 years ago and now have a world-famous business, have ceded management of the company to the family but are not yet ready to be put out to grass. On the contrary, they have set their sights sky high.
John McWilliams is also a keen pilot and as a former member of the RAF, he has returned to his first love with enthusiasm.
Flying, and more particularly gliding, is his thing now. (The wind socks, like the sails before them, are a lucrative by-product of making work out of a leisure pursuit.) To that end, the couple are moving to a more aerodrome-friendly environment. Wiltshire, to be exact.
This means their Sandycove home, with its precious site and sea views is now up for sale and is gliding in just under the million mark. Auctioneer, and neighbour, Pacelli Nolan of SWS Property Services Kinsale, gives a guide price of €985,000 for this simple but stylish property in the exclusive Kinsale enclave. There has already been interest in the property from potential buyers, she says.
The usual story applies here: you can't get planning on coastal sites because of visual amenity clauses and you can't get planning inland unless you're a farmer, or a relative of one.
The upshot of all this is that prices rocket for restricted areas. So Sandycove has seen some fine bidding spats in recent years, and the Mc Williams property should be no exception.
On a half-acre site, which is just about enough to be getting on with, the house is a modest-looking dwelling, but actually drops down to two levels at the rear and covers a very commodious 2,500 square feet of space.
It's south-facing with lovely gardens laid out all round and hedging to lessen the effect of the south-westerlies. There are interesting little spots throughout the grounds including two patio areas, a little orchard, fruit garden, vegetable patch and beds and borders.
The house is cottage-style to the front and is on the way to being covered with roses, hydrangeas and winter jasmine.
Seafield, as it's called, is a five-bedroom plus property which was remodelled internally by the Mc Williams when they moved here first. A relatively new property, Diana just added on to the existing layout and they converted the dormer portion which added much more space.
The couple lived at one end of the house while the work was carried out.
This area is effectively self-contained and includes independent access. Now used as an office space, it comes with a double, en suite bedroom and a large, kitchen/living room with sink and cooker fitted alongside computers, faxes and all the other paraphernalia of business life.
The rest of the house has a hand-built maple kitchen, a dining room, lounge, two bedrooms with shower room and utility on the ground floor.
Overhead is a main bathroom, a bedroom and a large, multi-purpose room. Two of the bedrooms are en suite.
The sale includes a huge garage and workshop which is deftly hidden behind high screens of fuchsia.