I have been persuaded that this excursion needs to be more Iron Butt like and specifically a full-blown coast-to-coast affair. This means moving the start to Ness Point (most easterly point of GB), 2.3 miles southeast of the hotel and the finish to Land's End (most westerly point of southern GB), 11.6 miles southwest of McDonalds. Those wishing to indulge in "touching the water" are on their own.
Curiously, Google offers a projection for NP-LE of only 431 miles instead of 432 for the original which you might expect to be 13.9 shorter but that's probably just as well as otherwise the additional 27.8 miles might prove too much for some entrants.