If I were to attempt this record, and I doubt I ever would, I probably wouldn't attempt it in the UK. Somewhere with a lot of flat land would seem to be preferable, such as the prairie states in the US. Start in a southern state and keep working west to east in corridors picking north to stay with the optimum weather and then south again hopefully avoiding any of the extreme weather events.
It's evidently doable, with better machinery, better nutrition and so on, just depends on someone being mad enough to do it. Would also benefit from a dedicated cycling meteorologist plotting the next days route in accordance with the anticipated weather patterns.
The question of verification would be to have a similarly sealed GPS unit that also took pictures of the person riding the bike and transmitted them to an open website. Technically hackable but at some point trust needs to come into it.